OverView
TextView应该是Android中最基础也是使用最广的控件，其能力简单来说就是将一段文本显示出来，但TextView可能也是最复杂的控件之一，涉及到的类众多，我们来采取自顶向下的方式来学习一下TextView的源码，这一篇先从最顶层开始，整体熟悉TextView的工作过程。
继承层次
public class TextView extends View implements ViewTreeObserver.OnPreDrawListener
继承层次很简单，是View的直接子类，实现了ViewTreeObserver.OnPreDrawListener接口
而在官方的文档中，能看到其子类有：
image.png
基础控件中常用的Button, EditText都是派生自TextView，这也说明了学习TextView的源码是大有裨益的。
构造函数
public TextView(Context context) {
this(context, null);
}
public TextView(Context context, @Nullable AttributeSet attrs) {
this(context, attrs, com.android.internal.R.attr.textViewStyle);
}
public TextView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
this(context, attrs, defStyleAttr, 0);
}
public TextView(
// ^
}
TextView的构造函数也是模板化的，有1~4个参数的构造函数，单参数的调用二参数然后以此类推，最终都会调用到4参数的构造函数
4参数的构造函数实现较长，分段来看下
super(context, attrs, defStyleAttr, defStyleRes);
// TextView is important by default, unless app developer overrode attribute.
if (getImportantForAutofill() == IMPORTANT_FOR_AUTOFILL_AUTO) {
setImportantForAutofill(IMPORTANT_FOR_AUTOFILL_YES);
}
setTextInternal("");
final Resources res = getResources();
final CompatibilityInfo compat = res.getCompatibilityInfo();
mTextPaint = new TextPaint(Paint.ANTI_ALIAS_FLAG);
mTextPaint.density = res.getDisplayMetrics().density;
mTextPaint.setCompatibilityScaling(compat.applicationScale);
mHighlightPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
mHighlightPaint.setCompatibilityScaling(compat.applicationScale);
mMovement = getDefaultMovementMethod();
mTransformation = null;
final TextAppearanceAttributes attributes = new TextAppearanceAttributes();
attributes.mTextColor = ColorStateList.valueOf(0xFF000000);
attributes.mTextSize = 15;
mBreakStrategy = Layout.BREAK_STRATEGY_SIMPLE;
mHyphenationFrequency = Layout.HYPHENATION_FREQUENCY_NONE;
mJustificationMode = Layout.JUSTIFICATION_MODE_NONE;
final Resources.Theme theme = context.getTheme();
- 第1部分主要是相关类和变量的初始化
TypedArray a = theme.obtainStyledAttributes(attrs,
com.android.internal.R.styleable.TextViewAppearance, defStyleAttr, defStyleRes);
TypedArray appearance = null;
int ap = a.getResourceId(
com.android.internal.R.styleable.TextViewAppearance_textAppearance, -1);
a.recycle();
if (ap != -1) {
appearance = theme.obtainStyledAttributes(
ap, com.android.internal.R.styleable.TextAppearance);
}
if (appearance != null) {
readTextAppearance(context, appearance, attributes, false /* styleArray */);
attributes.mFontFamilyExplicit = false;
appearance.recycle();
}
boolean editable = getDefaultEditable();
CharSequence inputMethod = null;
int numeric = 0;
CharSequence digits = null;
boolean phone = false;
boolean autotext = false;
int autocap = -1;
int buffertype = 0;
boolean selectallonfocus = false;
Drawable drawableLeft = null, drawableTop = null, drawableRight = null,
drawableBottom = null, drawableStart = null, drawableEnd = null;
ColorStateList drawableTint = null;
PorterDuff.Mode drawableTintMode = null;
int drawablePadding = 0;
int ellipsize = ELLIPSIZE_NOT_SET;
boolean singleLine = false;
int maxlength = -1;
CharSequence text = "";
CharSequence hint = null;
boolean password = false;
float autoSizeMinTextSizeInPx = UNSET_AUTO_SIZE_UNIFORM_CONFIGURATION_VALUE;
float autoSizeMaxTextSizeInPx = UNSET_AUTO_SIZE_UNIFORM_CONFIGURATION_VALUE;
float autoSizeStepGranularityInPx = UNSET_AUTO_SIZE_UNIFORM_CONFIGURATION_VALUE;
int inputType = EditorInfo.TYPE_NULL;
a = theme.obtainStyledAttributes(
attrs, com.android.internal.R.styleable.TextView, defStyleAttr, defStyleRes);
int firstBaselineToTopHeight = -1;
int lastBaselineToBottomHeight = -1;
int lineHeight = -1;
readTextAppearance(context, a, attributes, true /* styleArray */);
- 第2部分主要是获取应用的theme等全局属性，来初始化TextView的一些样式相关的变量
int n = a.getIndexCount();
// Must set id in a temporary variable because it will be reset by setText()
boolean textIsSetFromXml = false;
for (int i = 0; i < n; i++) {
int attr = a.getIndex(i);
switch (attr) {
case com.android.internal.R.styleable.TextView_editable:
editable = a.getBoolean(attr, editable);
break;
case com.android.internal.R.styleable.TextView_inputMethod:
inputMethod = a.getText(attr);
break;
case com.android.internal.R.styleable.TextView_numeric:
numeric = a.getInt(attr, numeric);
break;
// ……
case com.android.internal.R.styleable.TextView_lineHeight:
lineHeight = a.getDimensionPixelSize(attr, -1);
break;
}
}
a.recycle();
- 第3部分就是在XML中解析出对应的属性然后赋值到相关变量上
final int variation =
inputType & (EditorInfo.TYPE_MASK_CLASS | EditorInfo.TYPE_MASK_VARIATION);
final boolean passwordInputType = variation
== (EditorInfo.TYPE_CLASS_TEXT | EditorInfo.TYPE_TEXT_VARIATION_PASSWORD);
final boolean webPasswordInputType = variation
== (EditorInfo.TYPE_CLASS_TEXT | EditorInfo.TYPE_TEXT_VARIATION_WEB_PASSWORD);
final boolean numberPasswordInputType = variation
== (EditorInfo.TYPE_CLASS_NUMBER | EditorInfo.TYPE_NUMBER_VARIATION_PASSWORD);
final int targetSdkVersion = context.getApplicationInfo().targetSdkVersion;
mUseInternationalizedInput = targetSdkVersion >= VERSION_CODES.O;
mUseFallbackLineSpacing = targetSdkVersion >= VERSION_CODES.P;
if (inputMethod != null) {
Class<?> c;
try {
c = Class.forName(inputMethod.toString());
} catch (ClassNotFoundException ex) {
throw new RuntimeException(ex);
}
try {
createEditorIfNeeded();
mEditor.mKeyListener = (KeyListener) c.newInstance();
} catch (InstantiationException ex) {
throw new RuntimeException(ex);
} catch (IllegalAccessException ex) {
throw new RuntimeException(ex);
}
try {
mEditor.mInputType = inputType != EditorInfo.TYPE_NULL
? inputType
: mEditor.mKeyListener.getInputType();
} catch (IncompatibleClassChangeError e) {
mEditor.mInputType = EditorInfo.TYPE_CLASS_TEXT;
}
} else if (digits != null) {
createEditorIfNeeded();
mEditor.mKeyListener = DigitsKeyListener.getInstance(digits.toString());
// If no input type was specified, we will default to generic
// text, since we can't tell the IME about the set of digits
// that was selected.
mEditor.mInputType = inputType != EditorInfo.TYPE_NULL
? inputType : EditorInfo.TYPE_CLASS_TEXT;
} else if (inputType != EditorInfo.TYPE_NULL) {
setInputType(inputType, true);
// If set, the input type overrides what was set using the deprecated singleLine flag.
singleLine = !isMultilineInputType(inputType);
} else if (phone) {
createEditorIfNeeded();
mEditor.mKeyListener = DialerKeyListener.getInstance();
mEditor.mInputType = inputType = EditorInfo.TYPE_CLASS_PHONE;
} else if (numeric != 0) {
createEditorIfNeeded();
mEditor.mKeyListener = DigitsKeyListener.getInstance(
null, // locale
(numeric & SIGNED) != 0,
(numeric & DECIMAL) != 0);
inputType = mEditor.mKeyListener.getInputType();
mEditor.mInputType = inputType;
} else if (autotext || autocap != -1) {
TextKeyListener.Capitalize cap;
inputType = EditorInfo.TYPE_CLASS_TEXT;
switch (autocap) {
case 1:
cap = TextKeyListener.Capitalize.SENTENCES;
inputType |= EditorInfo.TYPE_TEXT_FLAG_CAP_SENTENCES;
break;
case 2:
cap = TextKeyListener.Capitalize.WORDS;
inputType |= EditorInfo.TYPE_TEXT_FLAG_CAP_WORDS;
break;
case 3:
cap = TextKeyListener.Capitalize.CHARACTERS;
inputType |= EditorInfo.TYPE_TEXT_FLAG_CAP_CHARACTERS;
break;
default:
cap = TextKeyListener.Capitalize.NONE;
break;
}
createEditorIfNeeded();
mEditor.mKeyListener = TextKeyListener.getInstance(autotext, cap);
mEditor.mInputType = inputType;
} else if (editable) {
createEditorIfNeeded();
mEditor.mKeyListener = TextKeyListener.getInstance();
mEditor.mInputType = EditorInfo.TYPE_CLASS_TEXT;
} else if (isTextSelectable()) {
// Prevent text changes from keyboard.
if (mEditor != null) {
mEditor.mKeyListener = null;
mEditor.mInputType = EditorInfo.TYPE_NULL;
}
bufferType = BufferType.SPANNABLE;
// So that selection can be changed using arrow keys and touch is handled.
setMovementMethod(ArrowKeyMovementMethod.getInstance());
} else {
if (mEditor != null) mEditor.mKeyListener = null;
switch (buffertype) {
case 0:
bufferType = BufferType.NORMAL;
break;
case 1:
bufferType = BufferType.SPANNABLE;
break;
case 2:
bufferType = BufferType.EDITABLE;
break;
}
}
if (mEditor != null) {
mEditor.adjustInputType(password, passwordInputType, webPasswordInputType,
numberPasswordInputType);
}
if (selectallonfocus) {
createEditorIfNeeded();
mEditor.mSelectAllOnFocus = true;
if (bufferType == BufferType.NORMAL) {
bufferType = BufferType.SPANNABLE;
}
}
- 第4部分是和输入编辑相关的初始化，涉及到的Editor类，负责的功能就是处理文本的区域选择处理和判断、拼写检查、弹出文本菜单等
// Set up the tint (if needed) before setting the drawables so that it
// gets applied correctly.
if (drawableTint != null || drawableTintMode != null) {
if (mDrawables == null) {
mDrawables = new Drawables(context);
}
if (drawableTint != null) {
mDrawables.mTintList = drawableTint;
mDrawables.mHasTint = true;
}
if (drawableTintMode != null) {
mDrawables.mTintMode = drawableTintMode;
mDrawables.mHasTintMode = true;
}
}
// This call will save the initial left/right drawables
setCompoundDrawablesWithIntrinsicBounds(
drawableLeft, drawableTop, drawableRight, drawableBottom);
setRelativeDrawablesIfNeeded(drawableStart, drawableEnd);
setCompoundDrawablePadding(drawablePadding);
- 第5部分的工作是，设置对应位置的Drawable
// Same as setSingleLine(), but make sure the transformation method and the maximum number
// of lines of height are unchanged for multi-line TextViews.
setInputTypeSingleLine(singleLine);
applySingleLine(singleLine, singleLine, singleLine);
if (singleLine && getKeyListener() == null && ellipsize == ELLIPSIZE_NOT_SET) {
ellipsize = ELLIPSIZE_END;
}
switch (ellipsize) {
case ELLIPSIZE_START:
setEllipsize(TextUtils.TruncateAt.START);
break;
case ELLIPSIZE_MIDDLE:
setEllipsize(TextUtils.TruncateAt.MIDDLE);
break;
case ELLIPSIZE_END:
setEllipsize(TextUtils.TruncateAt.END);
break;
case ELLIPSIZE_MARQUEE:
if (ViewConfiguration.get(context).isFadingMarqueeEnabled()) {
setHorizontalFadingEdgeEnabled(true);
mMarqueeFadeMode = MARQUEE_FADE_NORMAL;
} else {
setHorizontalFadingEdgeEnabled(false);
mMarqueeFadeMode = MARQUEE_FADE_SWITCH_SHOW_ELLIPSIS;
}
setEllipsize(TextUtils.TruncateAt.MARQUEE);
break;
}
final boolean isPassword = password || passwordInputType || webPasswordInputType
|| numberPasswordInputType;
final boolean isMonospaceEnforced = isPassword || (mEditor != null
&& (mEditor.mInputType
& (EditorInfo.TYPE_MASK_CLASS | EditorInfo.TYPE_MASK_VARIATION))
== (EditorInfo.TYPE_CLASS_TEXT | EditorInfo.TYPE_TEXT_VARIATION_PASSWORD));
if (isMonospaceEnforced) {
attributes.mTypefaceIndex = MONOSPACE;
}
applyTextAppearance(attributes);
if (isPassword) {
setTransformationMethod(PasswordTransformationMethod.getInstance());
}
if (maxlength >= 0) {
setFilters(new InputFilter[] { new InputFilter.LengthFilter(maxlength) });
} else {
setFilters(NO_FILTERS);
}
setText(text, bufferType);
if (textIsSetFromXml) {
mTextSetFromXmlOrResourceId = true;
}
if (hint != null) setHint(hint);
- 第6部分，是比较关键的设置文字的部分，先是确定好是否单行，然后设置省略方式，最后调用setText()，如果有必要还会设置hint
/*
* Views are not normally clickable unless specified to be.
* However, TextViews that have input or movement methods *are*
* clickable by default. By setting clickable here, we implicitly set focusable as well
* if not overridden by the developer.
*/
a = context.obtainStyledAttributes(
attrs, com.android.internal.R.styleable.View, defStyleAttr, defStyleRes);
boolean canInputOrMove = (mMovement != null || getKeyListener() != null);
boolean clickable = canInputOrMove || isClickable();
boolean longClickable = canInputOrMove || isLongClickable();
int focusable = getFocusable();
n = a.getIndexCount();
for (int i = 0; i < n; i++) {
int attr = a.getIndex(i);
switch (attr) {
case com.android.internal.R.styleable.View_focusable:
TypedValue val = new TypedValue();
if (a.getValue(attr, val)) {
focusable = (val.type == TypedValue.TYPE_INT_BOOLEAN)
? (val.data == 0 ? NOT_FOCUSABLE : FOCUSABLE)
: val.data;
}
break;
case com.android.internal.R.styleable.View_clickable:
clickable = a.getBoolean(attr, clickable);
break;
case com.android.internal.R.styleable.View_longClickable:
longClickable = a.getBoolean(attr, longClickable);
break;
}
}
a.recycle();
// Some apps were relying on the undefined behavior of focusable winning over
// focusableInTouchMode != focusable in TextViews if both were specified in XML (usually
// when starting with EditText and setting only focusable=false). To keep those apps from
// breaking, re-apply the focusable attribute here.
if (focusable != getFocusable()) {
setFocusable(focusable);
}
setClickable(clickable);
setLongClickable(longClickable);
- 第7部分是设置能否点击的相关属性
if (mEditor != null) mEditor.prepareCursorControllers();
// If not explicitly specified this view is important for accessibility.
if (getImportantForAccessibility() == IMPORTANT_FOR_ACCESSIBILITY_AUTO) {
setImportantForAccessibility(IMPORTANT_FOR_ACCESSIBILITY_YES);
}
if (supportsAutoSizeText()) {
if (mAutoSizeTextType == AUTO_SIZE_TEXT_TYPE_UNIFORM) {
// If uniform auto-size has been specified but preset values have not been set then
// replace the auto-size configuration values that have not been specified with the
// defaults.
if (!mHasPresetAutoSizeValues) {
final DisplayMetrics displayMetrics = getResources().getDisplayMetrics();
if (autoSizeMinTextSizeInPx == UNSET_AUTO_SIZE_UNIFORM_CONFIGURATION_VALUE) {
autoSizeMinTextSizeInPx = TypedValue.applyDimension(
TypedValue.COMPLEX_UNIT_SP,
DEFAULT_AUTO_SIZE_MIN_TEXT_SIZE_IN_SP,
displayMetrics);
}
if (autoSizeMaxTextSizeInPx == UNSET_AUTO_SIZE_UNIFORM_CONFIGURATION_VALUE) {
autoSizeMaxTextSizeInPx = TypedValue.applyDimension(
TypedValue.COMPLEX_UNIT_SP,
DEFAULT_AUTO_SIZE_MAX_TEXT_SIZE_IN_SP,
displayMetrics);
}
if (autoSizeStepGranularityInPx
== UNSET_AUTO_SIZE_UNIFORM_CONFIGURATION_VALUE) {
autoSizeStepGranularityInPx = DEFAULT_AUTO_SIZE_GRANULARITY_IN_PX;
}
validateAndSetAutoSizeTextTypeUniformConfiguration(autoSizeMinTextSizeInPx,
autoSizeMaxTextSizeInPx,
autoSizeStepGranularityInPx);
}
setupAutoSizeText();
}
} else {
mAutoSizeTextType = AUTO_SIZE_TEXT_TYPE_NONE;
}
if (firstBaselineToTopHeight >= 0) {
setFirstBaselineToTopHeight(firstBaselineToTopHeight);
}
if (lastBaselineToBottomHeight >= 0) {
setLastBaselineToBottomHeight(lastBaselineToBottomHeight);
}
if (lineHeight >= 0) {
setLineHeight(lineHeight);
}
- 最后第8部分是设置AutoSize/BaseLine/LineHeight等外观相关的属性
onMeasure()
对于onMeasure()源码的解析，同样还是分段来看：
int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int heightMode = MeasureSpec.getMode(heightMeasureSpec);
int widthSize = MeasureSpec.getSize(widthMeasureSpec);
int heightSize = MeasureSpec.getSize(heightMeasureSpec);
int width;
int height;
BoringLayout.Metrics boring = UNKNOWN_BORING;
BoringLayout.Metrics hintBoring = UNKNOWN_BORING;
if (mTextDir == null) {
mTextDir = getTextDirectionHeuristic();
}
- 第1部分是相关变量的初始化，这里涉及到一个BoringLayout的概念，在这一层先不去管其实现，知道它的作用是对最简单的文本进行排版
int des = -1;
boolean fromexisting = false;
final float widthLimit = (widthMode == MeasureSpec.AT_MOST)
? (float) widthSize : Float.MAX_VALUE;
if (widthMode == MeasureSpec.EXACTLY) {
// Parent has told us how big to be. So be it.
width = widthSize;
} else {
if (mLayout != null && mEllipsize == null) {
des = desired(mLayout);
}
if (des < 0) {
boring = BoringLayout.isBoring(mTransformed, mTextPaint, mTextDir, mBoring);
if (boring != null) {
mBoring = boring;
}
} else {
fromexisting = true;
}
if (boring == null || boring == UNKNOWN_BORING) {
if (des < 0) {
des = (int) Math.ceil(Layout.getDesiredWidthWithLimit(mTransformed, 0,
mTransformed.length(), mTextPaint, mTextDir, widthLimit));
}
width = des;
} else {
width = boring.width;
}
final Drawables dr = mDrawables;
if (dr != null) {
width = Math.max(width, dr.mDrawableWidthTop);
width = Math.max(width, dr.mDrawableWidthBottom);
}
if (mHint != null) {
int hintDes = -1;
int hintWidth;
if (mHintLayout != null && mEllipsize == null) {
hintDes = desired(mHintLayout);
}
if (hintDes < 0) {
hintBoring = BoringLayout.isBoring(mHint, mTextPaint, mTextDir, mHintBoring);
if (hintBoring != null) {
mHintBoring = hintBoring;
}
}
if (hintBoring == null || hintBoring == UNKNOWN_BORING) {
if (hintDes < 0) {
hintDes = (int) Math.ceil(Layout.getDesiredWidthWithLimit(mHint, 0,
mHint.length(), mTextPaint, mTextDir, widthLimit));
}
hintWidth = hintDes;
} else {
hintWidth = hintBoring.width;
}
if (hintWidth > width) {
width = hintWidth;
}
}
width += getCompoundPaddingLeft() + getCompoundPaddingRight();
if (mMaxWidthMode == EMS) {
width = Math.min(width, mMaxWidth * getLineHeight());
} else {
width = Math.min(width, mMaxWidth);
}
if (mMinWidthMode == EMS) {
width = Math.max(width, mMinWidth * getLineHeight());
} else {
width = Math.max(width, mMinWidth);
}
// Check against our minimum width
width = Math.max(width, getSuggestedMinimumWidth());
if (widthMode == MeasureSpec.AT_MOST) {
width = Math.min(widthSize, width);
}
}
int want = width - getCompoundPaddingLeft() - getCompoundPaddingRight();
int unpaddedWidth = want;
if (mHorizontallyScrolling) want = VERY_WIDE;
int hintWant = want;
int hintWidth = (mHintLayout == null) ? hintWant : mHintLayout.getWidth();
第2部分是对宽度的计算，如果MeasureMode是EXCACTLY，那直接用父View指定的宽度，否则需要通过Layout来计算，这里再重复一次Layout的概念——Layout负责TextView的排版，包括折行省略等；在计算宽度时，会在正文和hint都会产生一个对应的宽度，取两者最大值作为TextView的宽度
if (mLayout == null) {
makeNewLayout(want, hintWant, boring, hintBoring,
width - getCompoundPaddingLeft() - getCompoundPaddingRight(), false);
} else {
final boolean layoutChanged = (mLayout.getWidth() != want) || (hintWidth != hintWant)
|| (mLayout.getEllipsizedWidth()
!= width - getCompoundPaddingLeft() - getCompoundPaddingRight());
final boolean widthChanged = (mHint == null) && (mEllipsize == null)
&& (want > mLayout.getWidth())
&& (mLayout instanceof BoringLayout
|| (fromexisting && des >= 0 && des <= want));
final boolean maximumChanged = (mMaxMode != mOldMaxMode) || (mMaximum != mOldMaximum);
if (layoutChanged || maximumChanged) {
if (!maximumChanged && widthChanged) {
mLayout.increaseWidthTo(want);
} else {
makeNewLayout(want, hintWant, boring, hintBoring,
width - getCompoundPaddingLeft() - getCompoundPaddingRight(), false);
}
} else {
// Nothing has changed
}
}
- 第3部分也仍然是宽度的相关计算，根据Layout的内容对宽度进行调整，这里涉及到比较关键的方法是makeNewLayout()，关于这个方法，在下一层讲Layout时再展开说。
if (heightMode == MeasureSpec.EXACTLY) {
// Parent has told us how big to be. So be it.
height = heightSize;
mDesiredHeightAtMeasure = -1;
} else {
int desired = getDesiredHeight();
height = desired;
mDesiredHeightAtMeasure = desired;
if (heightMode == MeasureSpec.AT_MOST) {
height = Math.min(desired, heightSize);
}
}
int unpaddedHeight = height - getCompoundPaddingTop() - getCompoundPaddingBottom();
if (mMaxMode == LINES && mLayout.getLineCount() > mMaximum) {
unpaddedHeight = Math.min(unpaddedHeight, mLayout.getLineTop(mMaximum));
}
- 第4部分是对高度的计算，内容比宽度的处理少很多，主要通过getDesiredHeight()获得高度；篇幅比width少的原因在于，在计算width的时候，实际上已经通过Layout处理完了排版，完成了height所需的部分工作，getDesiredHeight()的内部实现实际上也是通过mLayout来获得高度的
/*
* We didn't let makeNewLayout() register to bring the cursor into view,
* so do it here if there is any possibility that it is needed.
*/
if (mMovement != null
|| mLayout.getWidth() > unpaddedWidth
|| mLayout.getHeight() > unpaddedHeight) {
registerForPreDraw();
} else {
scrollTo(0, 0);
}
setMeasuredDimension(width, height);
- 第5部分是最终width和height的结果处理
onLayout()
@Override
protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
super.onLayout(changed, left, top, right, bottom);
if (mDeferScroll >= 0) {
int curs = mDeferScroll;
mDeferScroll = -1;
bringPointIntoView(Math.min(curs, mText.length()));
}
// Call auto-size after the width and height have been calculated.
autoSizeText();
}
通常View的直接子类很少重写onLayout()函数，但TextView就重写了，主要工作就是在onLayout()中调用autoSizeText()
onDraw()
onDraw()函数同样也分段来看
restartMarqueeIfNeeded();
// Draw the background for this view
super.onDraw(canvas);
final int compoundPaddingLeft = getCompoundPaddingLeft();
final int compoundPaddingTop = getCompoundPaddingTop();
final int compoundPaddingRight = getCompoundPaddingRight();
final int compoundPaddingBottom = getCompoundPaddingBottom();
final int scrollX = mScrollX;
final int scrollY = mScrollY;
final int right = mRight;
final int left = mLeft;
final int bottom = mBottom;
final int top = mTop;
final boolean isLayoutRtl = isLayoutRtl();
final int offset = getHorizontalOffsetForDrawables();
final int leftOffset = isLayoutRtl ? 0 : offset;
final int rightOffset = isLayoutRtl ? offset : 0;
- 第1部分，是相关变量的初始化
final Drawables dr = mDrawables;
if (dr != null) {
/*
* Compound, not extended, because the icon is not clipped
* if the text height is smaller.
*/
int vspace = bottom - top - compoundPaddingBottom - compoundPaddingTop;
int hspace = right - left - compoundPaddingRight - compoundPaddingLeft;
// IMPORTANT: The coordinates computed are also used in invalidateDrawable()
// Make sure to update invalidateDrawable() when changing this code.
if (dr.mShowing[Drawables.LEFT] != null) {
canvas.save();
canvas.translate(scrollX + mPaddingLeft + leftOffset,
scrollY + compoundPaddingTop + (vspace - dr.mDrawableHeightLeft) / 2);
dr.mShowing[Drawables.LEFT].draw(canvas);
canvas.restore();
}
// IMPORTANT: The coordinates computed are also used in invalidateDrawable()
// Make sure to update invalidateDrawable() when changing this code.
if (dr.mShowing[Drawables.RIGHT] != null) {
canvas.save();
canvas.translate(scrollX + right - left - mPaddingRight
- dr.mDrawableSizeRight - rightOffset,
scrollY + compoundPaddingTop + (vspace - dr.mDrawableHeightRight) / 2);
dr.mShowing[Drawables.RIGHT].draw(canvas);
canvas.restore();
}
// IMPORTANT: The coordinates computed are also used in invalidateDrawable()
// Make sure to update invalidateDrawable() when changing this code.
if (dr.mShowing[Drawables.TOP] != null) {
canvas.save();
canvas.translate(scrollX + compoundPaddingLeft
+ (hspace - dr.mDrawableWidthTop) / 2, scrollY + mPaddingTop);
dr.mShowing[Drawables.TOP].draw(canvas);
canvas.restore();
}
// IMPORTANT: The coordinates computed are also used in invalidateDrawable()
// Make sure to update invalidateDrawable() when changing this code.
if (dr.mShowing[Drawables.BOTTOM] != null) {
canvas.save();
canvas.translate(scrollX + compoundPaddingLeft
+ (hspace - dr.mDrawableWidthBottom) / 2,
scrollY + bottom - top - mPaddingBottom - dr.mDrawableSizeBottom);
dr.mShowing[Drawables.BOTTOM].draw(canvas);
canvas.restore();
}
}
- 第2部分，对上下左右的Drawable进行绘制
int color = mCurTextColor;
if (mLayout == null) {
assumeLayout();
}
Layout layout = mLayout;
if (mHint != null && mText.length() == 0) {
if (mHintTextColor != null) {
color = mCurHintTextColor;
}
layout = mHintLayout;
}
mTextPaint.setColor(color);
mTextPaint.drawableState = getDrawableState();
canvas.save();
- 第3部分，确定此时绘制的是hint还是正文，设置对应的颜色和Layout
int extendedPaddingTop = getExtendedPaddingTop();
int extendedPaddingBottom = getExtendedPaddingBottom();
final int vspace = mBottom - mTop - compoundPaddingBottom - compoundPaddingTop;
final int maxScrollY = mLayout.getHeight() - vspace;
float clipLeft = compoundPaddingLeft + scrollX;
float clipTop = (scrollY == 0) ? 0 : extendedPaddingTop + scrollY;
float clipRight = right - left - getCompoundPaddingRight() + scrollX;
float clipBottom = bottom - top + scrollY
- ((scrollY == maxScrollY) ? 0 : extendedPaddingBottom);
if (mShadowRadius != 0) {
clipLeft += Math.min(0, mShadowDx - mShadowRadius);
clipRight += Math.max(0, mShadowDx + mShadowRadius);
clipTop += Math.min(0, mShadowDy - mShadowRadius);
clipBottom += Math.max(0, mShadowDy + mShadowRadius);
}
canvas.clipRect(clipLeft, clipTop, clipRight, clipBottom);
int voffsetText = 0;
int voffsetCursor = 0;
// translate in by our padding
/* shortcircuit calling getVerticaOffset() */
if ((mGravity & Gravity.VERTICAL_GRAVITY_MASK) != Gravity.TOP) {
voffsetText = getVerticalOffset(false);
voffsetCursor = getVerticalOffset(true);
}
canvas.translate(compoundPaddingLeft, extendedPaddingTop + voffsetText);
- 第4部分，是对padding的相关处理，主要是和阴影效果相关
final int layoutDirection = getLayoutDirection();
final int absoluteGravity = Gravity.getAbsoluteGravity(mGravity, layoutDirection);
if (isMarqueeFadeEnabled()) {
if (!mSingleLine && getLineCount() == 1 && canMarquee()
&& (absoluteGravity & Gravity.HORIZONTAL_GRAVITY_MASK) != Gravity.LEFT) {
final int width = mRight - mLeft;
final int padding = getCompoundPaddingLeft() + getCompoundPaddingRight();
final float dx = mLayout.getLineRight(0) - (width - padding);
canvas.translate(layout.getParagraphDirection(0) * dx, 0.0f);
}
if (mMarquee != null && mMarquee.isRunning()) {
final float dx = -mMarquee.getScroll();
canvas.translate(layout.getParagraphDirection(0) * dx, 0.0f);
}
}
- 第5部分，主要是走马灯效果的相关处理
final int cursorOffsetVertical = voffsetCursor - voffsetText;
Path highlight = getUpdatedHighlightPath();
if (mEditor != null) {
mEditor.onDraw(canvas, layout, highlight, mHighlightPaint, cursorOffsetVertical);
} else {
layout.draw(canvas, highlight, mHighlightPaint, cursorOffsetVertical);
}
if (mMarquee != null && mMarquee.shouldDrawGhost()) {
final float dx = mMarquee.getGhostOffset();
canvas.translate(layout.getParagraphDirection(0) * dx, 0.0f);
layout.draw(canvas, highlight, mHighlightPaint, cursorOffsetVertical);
}
canvas.restore();
- 第6部分，真正绘制文字的地方，实际上是通过mEditor.draw()或者layout.draw()来进行绘制
小结
在TextView这一层，整体流程如上文所示，从源码学习的过程中能看到，实际上测量和绘制的逻辑都在Layout/Editor这些类里面，在下一篇我们具体看下它们的实现。
