android->View(5)

View中的(0,0)坐标

public class MyView extends View{
    
    Paint paint;  //定义一个画笔
    public MyView(Context context){
       super(context);
    }
    
    // 初始化画笔
    public void intiPaint(){
        paint = new Paint();
        // 设置画笔
        paint.setColor(Color.GREEN);
        paint.setAntiAlias(true);
        paint.setStrokeWidth(5);    // 设置线宽
    }
    
    protected void onDraw(Canvas canvas){
       
       intiPaint();
       Resources rec = getResources();
       BitmapDrawable bitmapDrawable = (BitmapDrawable)rec.getDrawable(R.drawable.ss);
       Bitmap bitmap = bitmapDrawable.getBitmap();
       canvas.drawColor(Color.YELLOW);
       canvas.drawBitmap(bitmap, 20, 20,paint);
       canvas.drawLine(0, 0, this.getWidth(), this.getHeight(), paint);
    }
    
    /**
     * 这个是在XML中初始化用的
     * */
    public MyView(Context context,AttributeSet attrs){
       super(context, attrs);
    }

}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />
    <view class="com.example.customview.MyView"
        android:layout_width="100dip"
        android:layout_height="50dip" />

</LinearLayout>

效果图：