1.Android 中Stream 的使用(向下兼容)

step1：implementation 'com.annimon:stream:1.2.1'
step2：用法

ArrayList<User> arrayList = new ArrayList<>();
//从集合ArrayList中获取height>170 的数据集
List<User> users= Stream.of(arrayList).
    filter(user-> user.getHeight() > 170).
    collect(Collectors.toList());
//从ArrayList里获取姓名的集合
List<String> names = Stream.of(arrayList)
    .map(User::getName)
    .collect(Collectors.toList());
//取出User类中name重新构建成Customer的结合
List<Customer> userList = Stream.of(arrayList).
        map(user-> new Customer(user.getName())).
        collect(Collectors.toList());
//Sream返回的结果是List集合，如果你需要ArrayList集合，只需要强转类型即可
ArrayList<String> names = (ArrayList<String>) Stream.of(arrayList)
    .map(User::getName)
    .collect(Collectors.toList());

2.两个list进行“交集，并集，差集，去重复并集”的操作

//交集
addAll();
retainAll()；
//并集
addAll();
//差集
removeAll();
//去重复并集
removeAll();
addAll();

3.RecyclerView为网格布局添加间距

RecyclerView.ItemDecoration gridItemDecoration = new RecyclerView.ItemDecoration() {
            @Override
            public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
                StaggeredGridLayoutManager.LayoutParams layoutParams = (StaggeredGridLayoutManager.LayoutParams) view.getLayoutParams();
                int spanIndex = layoutParams.getSpanIndex();
                outRect.top = xx;
                if (spanIndex == 0) {
                    outRect.right = xx;
                } else {
                    outRect.left = xx;
                }
            }
        };
recyclerView.addItemDecoration(gridItemDecoration);

4.对一段文字进行拆分设置大小和加粗

public static void setGroupTextStyle(TextView textView, String frontText, int frontTextSize,
        boolean frontIsBold,String laterText, int laterTextSize, boolean laterIsBold) {
        if (frontText == null) {
            return;
        }
        String text = frontText + laterText;
        Spannable wordtoSpan = new SpannableString(text);
        wordtoSpan.setSpan(new AbsoluteSizeSpan(ScreenUtils.sp2px(BaseApplication.getContext(), frontTextSize)),
                0, frontText.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        if (frontIsBold) {
            wordtoSpan.setSpan(new StyleSpan(android.graphics.Typeface.BOLD),
                    0, frontText.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        }
        wordtoSpan.setSpan(new AbsoluteSizeSpan(ScreenUtils.sp2px(BaseApplication.getContext(), laterTextSize)),
                frontText.length(), text.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        if (laterIsBold) {
            wordtoSpan.setSpan(new StyleSpan(android.graphics.Typeface.BOLD),
                    frontText.length(), text.length(), Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
        }
        textView.setText(wordtoSpan);
    }

5.设置字体大小动态化

public static float getAdjustTvTextSize(TextView tv, int maxWidth, String text) {
        int avaiWidth = maxWidth - tv.getPaddingLeft() - tv.getPaddingRight();
        if (avaiWidth <= 0) {
            return 0f;
        }
        TextPaint textPaintClone = new TextPaint(tv.getPaint());
        // note that Paint text size works in px not sp
        float trySize = textPaintClone.getTextSize();
        while (textPaintClone.measureText(text) > avaiWidth) {
            trySize--;
            textPaintClone.setTextSize(trySize);
        }
        if (trySize > 0) {
            tv.setTextSize(TypedValue.COMPLEX_UNIT_PX, trySize);
        }
        return trySize;
    }

6.判断是否快速点击了，时间自定义

private static final int MIN_DELAY_TIME = 800;  //两次点击间隔不能少于800ms
    private static long lastClickTime;
    public static boolean isFastClick() {
        boolean flag = true;
        long currentClickTime = System.currentTimeMillis();
        if ((currentClickTime - lastClickTime) >= MIN_DELAY_TIME) {
            flag = false;
        }
        lastClickTime = currentClickTime;
        return flag;
    }

7.app整体置灰

第一种：基础封装类中重载此方法（类似BaseActivity类），替换根布局

    @Override
    public View onCreateView(String name, Context context, AttributeSet attrs) {
        try {
            if ("FrameLayout".equals(name)) {
                int count = attrs.getAttributeCount();
                for (int i = 0; i < count; i++) {
                    String attributeName = attrs.getAttributeName(i);
                    String attributeValue = attrs.getAttributeValue(i);
                    if (attributeName.equals("id")) {
                        int id = Integer.parseInt(attributeValue.substring(1));
                        String idVal = getResources().getResourceName(id);
                        if ("android:id/content".equals(idVal)) {
                            GrayFrameLayout grayFrameLayout = new GrayFrameLayout(context, attrs);
                            return grayFrameLayout;
                        }
                    }
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return super.onCreateView(name, context, attrs);
    }

 GrayFrameLayout ：
    public class GrayFrameLayout extends FrameLayout {
    private Paint mPaint = new Paint();
    public GrayFrameLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
        ColorMatrix cm = new ColorMatrix();
        cm.setSaturation(0);
        mPaint.setColorFilter(new ColorMatrixColorFilter(cm));
    }
    @Override
    protected void dispatchDraw(Canvas canvas) {
        canvas.saveLayer(null, mPaint, Canvas.ALL_SAVE_FLAG);
        super.dispatchDraw(canvas);
        canvas.restore();
    }
    @Override
    public void draw(Canvas canvas) {
        canvas.saveLayer(null, mPaint, Canvas.ALL_SAVE_FLAG);
        super.draw(canvas);
        canvas.restore();
    }
}

第二种：基础封装类中重载此方法，设置软硬件加速

    @Override
    protected void onStart() {
        super.onStart();
        View view = findViewById(android.R.id.content);
        if(view!=null){
            ColorMatrix cm = new ColorMatrix();
            cm.setSaturation(0);
            Paint mPaint = new Paint();
            mPaint.setColorFilter(new ColorMatrixColorFilter(cm));
            //setLayerType 软硬件加速看实际页面需要
            view.setLayerType(View.LAYER_TYPE_HARDWARE, mPaint);
        }
    }

8.app性能检测

第一种：
"Debug.startMethodTracing("App");"
---检测代码在这两个方法之间被包裹---
"Debug.stopMethodTracing();"
执行之后到android studio右下角的"Device File Explorer"中的
"sdcard/Android/data/项目包名/files"下的"App.trace"文件双击打开就行
第二种：
利用android studio的"profile插件"运行，利用"record和stop"记录分析文件