處理自定義視圖的事件(Event)

延伸前兩次文章"建立自定義視圖(Custom View)"和"通過XML調用自定義視圖(Custom View)", 本文示範如何處理自定義視圖的事件.



- 修改自定義視圖類, MyView.java, 重寫onTouchEvent(MotionEvent event)方法.

package com.AndroidView;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;
import android.widget.Toast;

public class MyView extends View {

private Paint myPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private Context myContext;

public MyView(Context context) {
 super(context);
 // TODO Auto-generated constructor stub
 myContext = context;
}

public MyView(Context context, AttributeSet attrs) {
 super(context, attrs);
 // TODO Auto-generated constructor stub
 myContext = context;
}

public MyView(Context context, AttributeSet attrs, int defStyle) {
 super(context, attrs, defStyle);
 // TODO Auto-generated constructor stub
 myContext = context;
}

@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
 // TODO Auto-generated method stub
 //super.onMeasure(widthMeasureSpec, heightMeasureSpec);

 setMeasuredDimension(MeasureSpec.getSize(widthMeasureSpec),
   MeasureSpec.getSize(heightMeasureSpec));
}

@Override
protected void onDraw(Canvas canvas) {
 // TODO Auto-generated method stub
 //super.onDraw(canvas);

 int radius;
 int height = getMeasuredHeight();
 int width = getMeasuredWidth();
 int centerX = width/2;
 int centerY = height/2;

 if (height>width){
  radius = width/2;
 }
 else{
  radius = height/2;
 }

 myPaint.setStyle(Paint.Style.STROKE);
 myPaint.setColor(Color.WHITE);

 myPaint.setStrokeWidth(1);
 canvas.drawLine(centerX, centerY-10, centerX, centerY+10, myPaint);
 canvas.drawLine(centerX-10, centerY, centerX+10, centerY, myPaint);

 myPaint.setStrokeWidth(10);
 myPaint.setColor(Color.RED);
 canvas.drawRect(0, 0, width, height, myPaint);

 myPaint.setStrokeWidth(3);
 myPaint.setColor(Color.GREEN);


 canvas.drawCircle(centerX, centerY, radius, myPaint);
}

@Override
public boolean onTouchEvent(MotionEvent event) {
 // TODO Auto-generated method stub

 int action = event.getAction();

 if (action == MotionEvent.ACTION_DOWN){
  Toast.makeText(myContext, "ACTION_DOWN", Toast.LENGTH_LONG).show();
 }
 else if (action == MotionEvent.ACTION_UP){
  Toast.makeText(myContext, "ACTION_UP", Toast.LENGTH_LONG).show();
 }

 return true;
}

}

next: 要強制重繪View，調用invalidate()