在对AlertDialog进行封装之前，我们有必要先了解一下AlertDialog的源码实现。一般情况下一行代码我们就可以创建一个弹框，如下所示：
new AlertDialog.Builder(this).create().show();
下面我们就一段段来分析，首先点击进去看下AlertDialog
public class AlertDialog extends AppCompatDialog implements DialogInterface {
...
}
public class AppCompatDialog extends Dialog implements AppCompatCallback {
...
}
也就是说我们的AlertDialog是继承自AppCompatDialog，而AppCompatDialog是继承自我们的Dialog，这个关系知道是怎么一回事就可以了，接下来进入到Builder里面。
public static class Builder {
private final AlertController.AlertParams P;
private final int mTheme;
/**
* Creates a builder for an alert dialog that uses the default alert
* dialog theme.
* <p>
* The default alert dialog theme is defined by
* {@link android.R.attr#alertDialogTheme} within the parent
* {@code context}'s theme.
*
* @param context the parent context
*/
public Builder(@NonNull Context context) {
this(context, resolveDialogTheme(context, 0));
}
/**
* Creates a builder for an alert dialog that uses an explicit theme
* resource.
* <p>
* The specified theme resource ({@code themeResId}) is applied on top
* of the parent {@code context}'s theme. It may be specified as a
* style resource containing a fully-populated theme, such as
* {@link R.style#Theme_AppCompat_Dialog}, to replace all
* attributes in the parent {@code context}'s theme including primary
* and accent colors.
* <p>
* To preserve attributes such as primary and accent colors, the
* {@code themeResId} may instead be specified as an overlay theme such
* as {@link R.style#ThemeOverlay_AppCompat_Dialog}. This will
* override only the window attributes necessary to style the alert
* window as a dialog.
* <p>
* Alternatively, the {@code themeResId} may be specified as {@code 0}
* to use the parent {@code context}'s resolved value for
* {@link android.R.attr#alertDialogTheme}.
*
* @param context the parent context
* @param themeResId the resource ID of the theme against which to inflate
* this dialog, or {@code 0} to use the parent
* {@code context}'s default alert dialog theme
*/
public Builder(@NonNull Context context, @StyleRes int themeResId) {
P = new AlertController.AlertParams(new ContextThemeWrapper(
context, resolveDialogTheme(context, themeResId)));
mTheme = themeResId;
}
...
}
可以看到，我们的Builder并不是直接在AlertDialog里面去创建方法，而是创建了一个静态内部类Builder，为什么会这样设计，了解设计模式的朋友可能会明白，这是用了建造者设计模式，便于为最后生成的AlertDialog进行个性化定制。在Builder里面有两个构造方法：
public Builder(@NonNull Context context) {
this(context, resolveDialogTheme(context, 0));
}
public Builder(@NonNull Context context, @StyleRes int themeResId) {
P = new AlertController.AlertParams(new ContextThemeWrapper(
context, resolveDialogTheme(context, themeResId)));
mTheme = themeResId;
}
注意看，第一个构造方法最终会执行到第二个构造方法里面，那么两个构造方法的区别是什么呢？注意看第二个构造方法的第二个参数themeResId，意思很明显AlertDialog的设置的主题，所以这里我们就很好去理解了，即：
在创建AlertDialog的Builder的时候，如果我们不给AlertDialog指定主题，则系统会默认使用系统自带的主题样式。
继续研究构造函数，里面有一个很重要的参数：P。这个P是在Builder里面声明的一个静态类：
public static class Builder {
private final AlertController.AlertParams P;
private final int mTheme;
在调用构造函数的时候会实例化P。那么这个P又是什么呢？点进去看看：
class AlertController {
...
public static class AlertParams {
public final Context mContext;
public final LayoutInflater mInflater;
}
}
可以很明显的看到，P是AlertController类里面的一个静态内部类，我们先知道这个概念，后面再详细介绍。
接下来我们进入到create方法
public AlertDialog create() {
// We can't use Dialog's 3-arg constructor with the createThemeContextWrapper param,
// so we always have to re-set the theme
final AlertDialog dialog = new AlertDialog(P.mContext, mTheme);
P.apply(dialog.mAlert);
dialog.setCancelable(P.mCancelable);
if (P.mCancelable) {
dialog.setCanceledOnTouchOutside(true);
}
dialog.setOnCancelListener(P.mOnCancelListener);
dialog.setOnDismissListener(P.mOnDismissListener);
if (P.mOnKeyListener != null) {
dialog.setOnKeyListener(P.mOnKeyListener);
}
return dialog;
}
我们一行一行来看：
首先创建了一个AlertDialog的实例
protected AlertDialog(@NonNull Context context, @StyleRes int themeResId) {
super(context, resolveDialogTheme(context, themeResId));
mAlert = new AlertController(getContext(), this, getWindow());
}
在这里创建了AlertController这个类，在AlertController这个构造方法里面主要是去设置一些属性
public AlertController(Context context, AppCompatDialog di, Window window) {
mContext = context;
mDialog = di;
mWindow = window;
mHandler = new ButtonHandler(di);
final TypedArray a = context.obtainStyledAttributes(null, R.styleable.AlertDialog,
R.attr.alertDialogStyle, 0);
mAlertDialogLayout = a.getResourceId(R.styleable.AlertDialog_android_layout, 0);
mButtonPanelSideLayout = a.getResourceId(R.styleable.AlertDialog_buttonPanelSideLayout, 0);
mListLayout = a.getResourceId(R.styleable.AlertDialog_listLayout, 0);
mMultiChoiceItemLayout = a.getResourceId(R.styleable.AlertDialog_multiChoiceItemLayout, 0);
mSingleChoiceItemLayout = a
.getResourceId(R.styleable.AlertDialog_singleChoiceItemLayout, 0);
mListItemLayout = a.getResourceId(R.styleable.AlertDialog_listItemLayout, 0);
mShowTitle = a.getBoolean(R.styleable.AlertDialog_showTitle, true);
mButtonIconDimen = a.getDimensionPixelSize(R.styleable.AlertDialog_buttonIconDimen, 0);
a.recycle();
/* We use a custom title so never request a window title */
di.supportRequestWindowFeature(Window.FEATURE_NO_TITLE);
}
继续向下看：
P.apply(dialog.mAlert);
public void apply(AlertController dialog) {
if (mCustomTitleView != null) {
dialog.setCustomTitle(mCustomTitleView);
} else {
if (mTitle != null) {
dialog.setTitle(mTitle);
}
if (mIcon != null) {
dialog.setIcon(mIcon);
}
if (mIconId != 0) {
dialog.setIcon(mIconId);
}
if (mIconAttrId != 0) {
dialog.setIcon(dialog.getIconAttributeResId(mIconAttrId));
}
}
if (mMessage != null) {
dialog.setMessage(mMessage);
}
if (mPositiveButtonText != null || mPositiveButtonIcon != null) {
dialog.setButton(DialogInterface.BUTTON_POSITIVE, mPositiveButtonText,
mPositiveButtonListener, null, mPositiveButtonIcon);
}
if (mNegativeButtonText != null || mNegativeButtonIcon != null) {
dialog.setButton(DialogInterface.BUTTON_NEGATIVE, mNegativeButtonText,
mNegativeButtonListener, null, mNegativeButtonIcon);
}
if (mNeutralButtonText != null || mNeutralButtonIcon != null) {
dialog.setButton(DialogInterface.BUTTON_NEUTRAL, mNeutralButtonText,
mNeutralButtonListener, null, mNeutralButtonIcon);
}
// For a list, the client can either supply an array of items or an
// adapter or a cursor
if ((mItems != null) || (mCursor != null) || (mAdapter != null)) {
createListView(dialog);
}
if (mView != null) {
if (mViewSpacingSpecified) {
dialog.setView(mView, mViewSpacingLeft, mViewSpacingTop, mViewSpacingRight,
mViewSpacingBottom);
} else {
dialog.setView(mView);
}
} else if (mViewLayoutResId != 0) {
dialog.setView(mViewLayoutResId);
}
/*
dialog.setCancelable(mCancelable);
dialog.setOnCancelListener(mOnCancelListener);
if (mOnKeyListener != null) {
dialog.setOnKeyListener(mOnKeyListener);
}
*/
}
首先在AlertController类里面的静态内部类AlertParams里调用了apply方法，而在这个方法里面其实不难看出是给我们的AlertController里面的属性赋值，而值是来自于AlertParams声明的属性。其他的几行代码很好理解，就是给我们的AlertDialog设置监听，最后返回AlertDialog实例，最后调用show方法进行展示即可。
到这里，AlertDialog的源码我们大致走了一遍，我们可以大致梳理一下其中几个关键类的关系。
1.png
AlertController：顾名思义AlertDialog的控制器类，主要是用于处理AlertDialog的各种系统内置属性，持有AlertDialog的实例。
AlertParams：AlertController的内部类，是一个static的类，声明各种通用的属性，比如文本，图片，视图等等。在执行apply方法的时候，将获取的值传递给AlertController。
Builder：AlertDialog的内部类，是一个static的类，用于构建AlertDialog。同时持有AlertController.AlertParams的实例。
了解了这几个类的主要作用，接下来我们就通过一个具体的实例来看看AlertDialog到底是怎么运行的，简单例子：
val dialog = AlertDialog.Builder(this)
dialog.setIcon(R.mipmap.ic_launcher)
dialog.setTitle("对话框")
dialog.setMessage("这是一个普通的对话框")
dialog.show()
一步一步分析：
val dialog = AlertDialog.Builder(this)
调用AlertDialog内部类Builder类的构造方法，实例化AlertController.AlertParams类
dialog.setIcon(R.mipmap.ic_launcher)
dialog.setTitle("对话框")
dialog.setMessage("这是一个普通的对话框")
给AlertController.AlertParams类里面的图标、标题、信息设置具体的值。
dialog.show()
这个会是分析的重点：
（1）首先会去执行AlertDialog.Builder类里面的show()方法
public AlertDialog show() {
final AlertDialog dialog = create();
dialog.show();
return dialog;
}
（2）进入create方法
@NonNull
public AlertDialog create() {
// We can't use Dialog's 3-arg constructor with the createThemeContextWrapper param,
// so we always have to re-set the theme
final AlertDialog dialog = new AlertDialog(P.mContext, mTheme);
P.apply(dialog.mAlert);
dialog.setCancelable(P.mCancelable);
if (P.mCancelable) {
dialog.setCanceledOnTouchOutside(true);
}
dialog.setOnCancelListener(P.mOnCancelListener);
dialog.setOnDismissListener(P.mOnDismissListener);
if (P.mOnKeyListener != null) {
dialog.setOnKeyListener(P.mOnKeyListener);
}
return dialog;
}
首先创建AlertDialog的实例，然后最终将这个实例返回，P是在Builder的时候就会被实例化的AlertController.AlertParams实例。接着执行AlertController.AlertParams的apply方法，在这里将我们赋值的title、message和icon赋值给AlertController，也可以理解为对AlertController进行封装，接下来继续对AlertDialog的各种回调进行监听。
（2）继续执行到show()方法
public void show() {
if (mShowing) {
if (mDecor != null) {
if (mWindow.hasFeature(Window.FEATURE_ACTION_BAR)) {
mWindow.invalidatePanelMenu(Window.FEATURE_ACTION_BAR);
}
mDecor.setVisibility(View.VISIBLE);
}
return;
}
mCanceled = false;
if (!mCreated) {
dispatchOnCreate(null);
} else {
// Fill the DecorView in on any configuration changes that
// may have occured while it was removed from the WindowManager.
final Configuration config = mContext.getResources().getConfiguration();
mWindow.getDecorView().dispatchConfigurationChanged(config);
}
onStart();
mDecor = mWindow.getDecorView();
if (mActionBar == null && mWindow.hasFeature(Window.FEATURE_ACTION_BAR)) {
final ApplicationInfo info = mContext.getApplicationInfo();
mWindow.setDefaultIcon(info.icon);
mWindow.setDefaultLogo(info.logo);
mActionBar = new WindowDecorActionBar(this);
}
WindowManager.LayoutParams l = mWindow.getAttributes();
boolean restoreSoftInputMode = false;
if ((l.softInputMode
& WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION) == 0) {
l.softInputMode |=
WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION;
restoreSoftInputMode = true;
}
mWindowManager.addView(mDecor, l);
if (restoreSoftInputMode) {
l.softInputMode &=
~WindowManager.LayoutParams.SOFT_INPUT_IS_FORWARD_NAVIGATION;
}
mShowing = true;
sendShowMessage();
}
首先判断有没有被创建过，也可以理解为AlertDialog所对应的视图部分，如果没有，执行
dispatchOnCreate(null)方法
void dispatchOnCreate(Bundle savedInstanceState) {
if (!mCreated) {
onCreate(savedInstanceState);
mCreated = true;
}
}
在这个方法里面会去执行onCreate(savedInstanceState)方法，所以我们找到AlertDialog的onCreate(savedInstanceState)方法
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mAlert.installContent();
}
在这个方法里面最终会执行到AlertController的installContent方法
public void installContent() {
final int contentView = selectContentView();
mDialog.setContentView(contentView);
setupView();
}
这个方法比较重要，首先是通过selectContentView()获取到我们的View，然后将View添加到mDialog里面去，最终执行setupView()方法对这个视图赋值，最后调用
mWindowManager.addView(mDecor, l);
将页面进行展示出来。大概的时序图为:
2.png
了解了原理之后，我们就开始进入实战部分了
首先类的结构如下所示：
3.png
首先创建AlertController类，主要的功能有：
（1）持有AlertDialog的实例
（2）创建内部类AlertParams
class AlertController {
private AlertDialog mDialog;
private Window mWindow;
private DialogViewHelper mViewHelper;
public AlertController(AlertDialog dialog, Window window) {
this.mDialog = dialog;
this.mWindow = window;
}
public AlertDialog getDialog() {
return mDialog;
}
public Window getWindow() {
return mWindow;
}
// 设置TextView
public void setText(int viewId, CharSequence text) {
mViewHelper.setText(viewId, text);
}
public void setViewHelper(DialogViewHelper viewHelper) {
this.mViewHelper = viewHelper;
}
// 设置点击事件
public void setOnClickListener(int viewId, View.OnClickListener listener) {
mViewHelper.setOnClickListener(viewId, listener);
}
public <T extends View> T getView(int viewId) {
return mViewHelper.getView(viewId);
}
public static class AlertParams {
public Context mContext;
public int mThemeResId;
// 点击空白区是否可以取消
public boolean mCancelable = true;
// dialog cancel监听
public DialogInterface.OnCancelListener mOnCancelListener;
// dialog dismiss 监听
public DialogInterface.OnDismissListener mOnDismissListener;
// dialog 按键监听
public DialogInterface.OnKeyListener mOnKeyListener;
// 布局View
public View mView;
// 布局LayoutId
public int mViewLayoutResId;
// 存放所有的文本
public SparseArray<CharSequence> mTextArray = new SparseArray<>();
// 存放所有的点击事件
public SparseArray<View.OnClickListener> mClickArray = new SparseArray<>();
// 设置宽度
public int mWidth = ViewGroup.LayoutParams.WRAP_CONTENT;
// 设置动画
public int mAnimations = 0;
// 设置从底部弹出
public int mGravity = Gravity.CENTER;
// 设置高度
public int mHeight = ViewGroup.LayoutParams.WRAP_CONTENT;
public AlertParams(Context context, int themeResId) {
this.mContext = context;
this.mThemeResId = themeResId;
}
// 绑定和设置参数
public void apply(AlertController mAlert) {
DialogViewHelper viewHelper = null;
// 设置布局
if (mViewLayoutResId != 0) {
viewHelper = new DialogViewHelper(mContext, mViewLayoutResId);
}
if (mView != null) {
viewHelper = new DialogViewHelper();
viewHelper.setContentView(mView);
}
mAlert.setViewHelper(viewHelper);
if (viewHelper == null) {
throw new IllegalArgumentException("请设置布局setContentView()");
}
// 给Dialog设置布局
mAlert.getDialog().setContentView(viewHelper.getContentView());
// 设置文本
int textArraySize = mTextArray.size();
for (int i = 0; i < textArraySize; i++) {
viewHelper.setText(mTextArray.keyAt(i), mTextArray.valueAt(i));
}
// 设置点击事件
int textClickSize = mClickArray.size();
for (int i = 0; i < textClickSize; i++) {
viewHelper.setOnClickListener(mClickArray.keyAt(i), mClickArray.valueAt(i));
}
Window window = mAlert.getWindow();
window.setGravity(mGravity);
if (mAnimations != 0)
window.setWindowAnimations(mAnimations);
WindowManager.LayoutParams params = window.getAttributes();
params.width = mWidth;
params.height = mHeight;
window.setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
window.setAttributes(params);
}
}
}
创建AlertDialog继承自Dialog，其包含的主要内容有：
（1）持有AlertController的实例
（2）创建内部类Builder
public class AlertDialog extends Dialog {
final AlertController mAlert;
public AlertDialog(@NonNull Context context) {
this(context, 0);
}
public AlertDialog(@NonNull Context context, @StyleRes int themeResId) {
super(context, themeResId);
mAlert = new AlertController(this, getWindow());
}
// 设置TextView
public void setText(int viewId, CharSequence text) {
mAlert.setText(viewId, text);
}
// 设置点击事件
public void setOnClickListener(int viewId, View.OnClickListener listener) {
mAlert.setOnClickListener(viewId, listener);
}
public <T extends View> T getView(int viewId) {
return mAlert.getView(viewId);
}
public static class Builder {
private final AlertController.AlertParams P;
public Builder(@NonNull Context context) {
this(context, R.style.MyDialog);
}
public Builder(@NonNull Context context, @StyleRes int themeResId) {
P = new AlertController.AlertParams(context, themeResId);
P.mThemeResId = themeResId;
}
// 设置View
public Builder setContentView(int layoutResId) {
P.mView = null;
P.mViewLayoutResId = layoutResId;
return this;
}
// 设置View
public Builder setContentView(View view) {
P.mView = view;
P.mViewLayoutResId = 0;
return this;
}
// 设置文本
public Builder setText(int viewId, CharSequence text) {
P.mTextArray.put(viewId, text);
return this;
}
// 设置全屏
public Builder fullWith() {
P.mWidth = ViewGroup.LayoutParams.MATCH_PARENT;
return this;
}
// 设置动画
public Builder fromBottom(boolean isAnimation) {
if (isAnimation) {
P.mAnimations = R.style.dialog_from_bottom_anim;
}
P.mGravity = Gravity.BOTTOM;
return this;
}
// 设置Dialog的宽高
public Builder setWidthAndHeight(int width, int height) {
P.mWidth = width;
P.mHeight = height;
return this;
}
// 设置默认动画
public Builder addDefaultAnimation() {
P.mAnimations = R.style.dialog_scale_anim;
return this;
}
// 添加动画
public Builder setAnimations(int styleAnimation) {
P.mAnimations = styleAnimation;
return this;
}
// 设置点击事件
public Builder setOnClickListener(int viewId, View.OnClickListener listener) {
P.mClickArray.put(viewId, listener);
return this;
}
public Builder setCancelable(boolean cancelable) {
P.mCancelable = cancelable;
return this;
}
public Builder setOnCancelListener(OnCancelListener onCancelListener) {
P.mOnCancelListener = onCancelListener;
return this;
}
public Builder setOnDismissListener(OnDismissListener onDismissListener) {
P.mOnDismissListener = onDismissListener;
return this;
}
public Builder setOnKeyListener(OnKeyListener onKeyListener) {
P.mOnKeyListener = onKeyListener;
return this;
}
public AlertDialog create() {
final AlertDialog dialog = new AlertDialog(P.mContext, P.mThemeResId);
P.apply(dialog.mAlert);
dialog.setCancelable(P.mCancelable);
if (P.mCancelable) {
dialog.setCanceledOnTouchOutside(true);
}
dialog.setOnCancelListener(P.mOnCancelListener);
dialog.setOnDismissListener(P.mOnDismissListener);
if (P.mOnKeyListener != null) {
dialog.setOnKeyListener(P.mOnKeyListener);
}
return dialog;
}
public AlertDialog show() {
final AlertDialog dialog = create();
dialog.show();
return dialog;
}
}
}
最后附上我们的DialogViewHelper处理类
public class DialogViewHelper {
private View mContentView = null;
private SparseArray<WeakReference<View>> mViews;
public DialogViewHelper(Context mContext, int mViewLayoutResId) {
this();
mContentView = LayoutInflater.from(mContext).inflate(mViewLayoutResId, null);
}
public DialogViewHelper() {
mViews = new SparseArray<>();
}
// 设置布局
public void setContentView(View mView) {
this.mContentView = mView;
}
// 设置TextView
public void setText(int viewId, CharSequence text) {
TextView tv = getView(viewId);
if (tv != null) {
tv.setText(text);
}
}
// 设置点击事件
public void setOnClickListener(int viewId, View.OnClickListener listener) {
View tv = getView(viewId);
if (tv != null) {
tv.setOnClickListener(listener);
}
}
public <T extends View> T getView(int viewId) {
WeakReference<View> viewReference = mViews.get(viewId);
View view = null;
if (viewReference != null) {
view = viewReference.get();
}
if (view == null) {
view = mContentView.findViewById(viewId);
if (view != null)
mViews.put(viewId, new WeakReference<>(view));
}
return (T) view;
}
// 获取Content内容的View
public View getContentView() {
return mContentView;
}
}
到这里，一个根据AlertDialog源码搭建的通用型AlertDialog就搭建完成啦。
最后附上一个使用例子：
new AlertDialog.Builder(this)
.setContentView(R.layout.item_permission)
.setText(R.id.item_delete_content, getString(R.string.sure_refruse_permission))
.setOnClickListener(R.id.item_delete_cancel, new NoDoubleClickListener() {
@Override
public void onNoDoubleClick(View v) {
if (mXXPermissions != null && mXXPermissions.isShowing()) {
mXXPermissions.dismiss();
}
Util.checkPermission(MainActivity.this);
}
})
.setOnClickListener(R.id.item_delete_sure, new NoDoubleClickListener() {
@Override
public void onNoDoubleClick(View v) {
if (mXXPermissions != null && mXXPermissions.isShowing()) {
mXXPermissions.dismiss();
}
requestPermission();
}
})
.setCancelable(false)
.fullWith()
.create();
