的onDraw（）进行查看 [英] onDraw() for View

问题描述

我只是在我的布局文件中创建一个视图位置：

I just created one view in my layout file here:

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_height="match_parent" android:layout_width="match_parent">
    <com.shawntesting.MyView android:layout_above="@+id/button1" android:layout_alignParentTop="true" android:layout_height="match_parent" android:layout_width="match_parent" android:id="@+id/myview1"></com.shawntesting.MyView>
    <Button android:id="@+id/button1" android:layout_height="wrap_content" android:layout_width="wrap_content" android:text="Button" android:layout_alignParentBottom="true" ></Button>
    <Button android:id="@+id/button2" android:text="button2" android:layout_alignParentBottom="true" android:layout_toRightOf="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content"></Button>
</RelativeLayout>

这是我的看法code：

And this is my view code:

    public class MyView extends View{



   Paint paint;


   public MyView(Context context, AttributeSet attrs){ 
       super(context,attrs);
       paint=new Paint();
       paint.setColor(Color.WHITE);

   }


   public void setblue(){

      paint.setColor(Color.BLUE);
      this.postInvalidate();

   }
   public void setgreen(){

       paint.setColor(Color.GREEN);
       this.postInvalidate();
   }

  public void onDraw(Canvas canvas){     
          super.onDraw(canvas);
            canvas.drawRect(x, y, 100, 50, paint);
            String i=new String();
            Log.i("getColor",i.valueOf(paint.getColor()));


       }

}

和最后一个是我的主要活动：

And last is my main activity:

    public class Activity2 extends Activity{
    MyView mv;
    AttributeSet attributes;
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        XmlPullParser parser = getResources().getXml(R.layout.main);
         attributes = Xml.asAttributeSet(parser);
         mv=new MyView(this,attributes);

        setContentView(R.layout.main);
        Button b1=(Button)findViewById(R.id.button1);
        Button b2=(Button)findViewById(R.id.button2);
        b1.setOnClickListener(new Button.OnClickListener(){

            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                mv.setblue();
                //mv=(MyView)findViewById(R.id.myview1);
                //mv.invalidate();

            }

        });
        b2.setOnClickListener(new Button.OnClickListener(){

            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                mv.setgreen();
                //mv=(MyView)findViewById(R.id.myview1);
                //mv.invalidate();

            }

        });
    }
}

我的问题是点击按钮后，视图不会刷新。
而且我还发现，点击按钮后，的onDraw（）正在执行2倍（第一为preSS按住按钮，第二松动的点击）为什么会发生？

My question is after clicking the button, the view is not refreshed. And i also found that after clicking the button, the onDraw() is performing 2times(first for press down the button,second for loose the clicking) why that happened?

推荐答案

这是因为你正在创建MyView的的第二个实例。你需要做出MyView的参考这是您的布局：

This is because you are creating the second instance of MyView. You need to make a reference to MyView which is in your layout:

MyView mv;  
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    setContentView(R.layout.main);

    mv = (MyView) findViewById(R.id.myview1);
    Button b1=(Button)findViewById(R.id.button1); 
    Button b2=(Button)findViewById(R.id.button2); 

    b1.setOnClickListener(new Button.OnClickListener(){ 

        public void onClick(View arg0) { 

            mv.setblue(); 

        } 

    }); 
    b2.setOnClickListener(new Button.OnClickListener(){ 

        public void onClick(View arg0) { 

            mv.setgreen(); 

        } 

    }); 
} 

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