最近较流行的效果 Android自定义View实现倾斜列表/图片

先看看效果图：

实现思路：擦除图片相应的角，然后层叠图片，产生倾斜效果

代码实现：

1、定义属性

在values文件夹下的attrs文件添加以下代码

<resources>
  <declare-styleable name="TiltView">
    <attr name="type" format="integer" />
  </declare-styleable>
</resources>

2、自定义布局

public class TiltView extends ImageView {
  private int imageWidth;//图片宽度
  private int imageHeight;//图片高度
  private double angle = 10 * Math.PI / 180;//三角形角度
  private int triangleHeight;//三角形高度
  private Paint paint;//画笔
  private Path path;//绘制路径
  private int type;//倾斜图片的类型
  public TiltView(Context context) {
    this(context, null);
  }
  public TiltView(Context context, AttributeSet attrs) {
    this(context, attrs, 0);
  }
  public TiltView(Context context, AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    TypedArray array = context.obtainStyledAttributes(attrs, R.styleable.TiltView);
    type = array.getInteger(R.styleable.TiltView_type, 1);
    array.recycle();
  }
  //重测大小
  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    imageWidth = measureSpec(widthMeasureSpec);
    imageHeight = measureSpec(heightMeasureSpec);
    setMeasuredDimension(imageWidth, imageHeight); //设置View的大小
    triangleHeight = (int) (Math.abs(Math.tan(angle) * imageHeight));
  }
  //测量长度
  private int measureSpec(int measureSpec) {
    int minLength = 200;
    int mode = MeasureSpec.getMode(measureSpec);
    int length = MeasureSpec.getSize(measureSpec);
    if (mode == MeasureSpec.AT_MOST) {
      length = Math.min(length, minLength);
    }
    return length;
  }
  @Override
  protected void onDraw(Canvas canvas) {
    initPaint();
    Bitmap mBitmap = Bitmap.createBitmap(imageWidth, imageHeight, Bitmap.Config.ARGB_8888); //初始化Bitmap
    Canvas mCanvas = new Canvas(mBitmap);//创建画布，并绘制mBitmap
    Bitmap mBackBitmap = ((BitmapDrawable) getDrawable()).getBitmap();
    mCanvas.drawBitmap(resizeBitmap(mBackBitmap), 0, 0, null);//绘制Bitmap
    setTriangle();
    paint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_OUT));
    mCanvas.drawPath(path, paint);
    canvas.drawBitmap(mBitmap, 0, 0, null);
  }
  //初始化画笔
  private void initPaint() {
    paint = new Paint();
    paint.setDither(true);//设定是否使用图像抖动处理，会使绘制出来的图片颜色更加平滑和饱满，图像更加清晰
    paint.setAntiAlias(true);//设置抗锯齿
    paint.setStrokeWidth(5);
    paint.setStyle(Paint.Style.FILL);
    paint.setStrokeCap(Paint.Cap.ROUND);
    paint.setStrokeJoin(Paint.Join.ROUND);//圆角
  }
  //设置三角形区域
  private void setTriangle() {
    path = new Path();
    switch (type) {
      case 1://右下角
        path.moveTo(0, imageHeight);
        path.lineTo(imageWidth, imageHeight);
        path.lineTo(imageWidth, imageHeight - triangleHeight);
        path.lineTo(0, imageHeight);
        break;
      case 2://左上角+左下角
        path.moveTo(0, triangleHeight);
        path.lineTo(imageWidth, 0);
        path.lineTo(0, 0);
        path.lineTo(0, imageHeight);
        path.lineTo(imageWidth, imageHeight);
        path.lineTo(0, imageHeight - triangleHeight);
        break;
      case 3://右上角+右下角
        path.moveTo(imageWidth, triangleHeight);
        path.lineTo(0, 0);
        path.lineTo(imageWidth, 0);
        path.lineTo(imageWidth, imageHeight);
        path.lineTo(0, imageHeight);
        path.lineTo(imageWidth, imageHeight - triangleHeight);
        break;
      case 4://右上角
        path.moveTo(0, 0);
        path.lineTo(imageWidth, 0);
        path.lineTo(imageWidth, triangleHeight);
        path.lineTo(0, 0);
        break;
      case 5://左上角
        path.moveTo(0, 0);
        path.lineTo(imageWidth, 0);
        path.lineTo(0, triangleHeight);
        path.lineTo(0, 0);
        break;
    }
  }
  //重新调节图片大小
  private Bitmap resizeBitmap(Bitmap bitmap) {
    int width = bitmap.getWidth();
    int height = bitmap.getHeight();
    // 设置想要的大小
    int newWidth = imageWidth;
    int newHeight = imageHeight;
    // 计算缩放比例
    float scaleWidth = ((float) newWidth) / width;
    float scaleHeight = ((float) newHeight) / height;
    // 取得想要缩放的matrix参数
    Matrix matrix = new Matrix();
    matrix.postScale(scaleWidth, scaleHeight);
    // 得到新的图片
    return Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true);
  }
}

3、布局代码调用

//其中android:layout_marginTop="-15dp"对效果实现有很大的作用
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
  xmlns:app="http://schemas.android.com/apk/res-auto"
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  android:orientation="vertical">
  <com.pengkv.may.widget.TiltView
    android:layout_width="match_parent"
    android:layout_height="100dp"
    android:src="@drawable/sample_0"
    app:type="1" />
  <com.pengkv.may.widget.TiltView
    android:layout_width="match_parent"
    android:layout_height="100dp"
    android:layout_marginTop="-15dp"
    android:src="@drawable/sample_1"
    app:type="2" />
  <com.pengkv.may.widget.TiltView
    android:layout_width="match_parent"
    android:layout_height="100dp"
    android:layout_marginTop="-15dp"
    android:src="@drawable/sample_2"
    app:type="4" />
</LinearLayout>

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