public class SquareImageView extends View {
    private Paint mPaint;
    private Bitmap bitmap;
    int left;
    int top;
    //這個構造方法，是new物件，例項化物件的時候呼叫的，
/*    public SquareImageView(Context context) {
        super(context);
        mPaint=new Paint();
    }*/

    //這個構造方法，是在你的xml檔案中呼叫的方法，就是在xml檔案裡寫上全類名，當作元件用
    public SquareImageView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        mPaint=new Paint();
        bitmap= BitmapFactory.decodeFile("/storage/sdcard0/BIG-BANNER-YYSYHF.jpg");

        //獲取自定義屬性陣列
        TypedArray array = context.getTheme().obtainStyledAttributes(attrs,R.styleable.SquareImageView,0,0);
        //獲取具體的自定義屬性
        int color=array.getColor(R.styleable.SquareImageView_paintColor,0x000000);
        //獲取具體的自定義屬性
        left= array.getInteger(R.styleable.SquareImageView_left,100);
        //使用xml裡自定義屬性的值
        mPaint.setColor(color);

    }

    public SquareImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    public SquareImageView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    //view的繪製流程，分為onMeasure（測量獲得元件的尺寸，提供給onLayout使用，onLayout還不一定使用）
    //onLayout 佈局，知道設定元件的位置
    // ondraw()把元件畫出來
    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawBitmap(drawSquare(left),0,0,mPaint);

    }
  public Bitmap drawSquare(int left){
      Paint paint=new Paint();
      paint.setColor(Color.YELLOW);
      Rect rect=new Rect(left,50,0,0);
      Bitmap bm=Bitmap.createBitmap(bitmap.getWidth(),bitmap.getHeight().Config.ARGB_8888);
      Canvas canvas=new Canvas(bm);
    //  canvas.drawRect(rect,paint);
      canvas.drawBitmap(bitmap,0,0,paint);
      return  bm;
  }

//在res/values/attrs.xml裡新增
<declare-styleable name="SquareImageView">
    <attr name="left" format="integer"/>
    <attr name="paintColor" format="color"/>
</declare-styleable>

//定義一個命名控制元件
xmlns:app="http://schemas.android.com/apk/res-auto"

//使用自定義view
<com.example.*****.view.SquareImageView
    android:id="@+id/freeview"
    app:left="150" //使用屬性
    app:paintColor="@color/colorPrimaryDark" //使用屬性
    android:layout_width="match_parent"
    android:layout_height="300dp">
</com.example.*****.view.SquareImageView>

}