用如下代码画一个圆为什么会出错啊?正确的代码应该怎样写?请高手赐教!!!
package com.mjl.gameView;import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;public class GameView extends View{ Context context = null;
public GameView(Context context) {
super(context);
// TODO Auto-generated constructor stub
this.context=context;
}
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
super.onDraw(canvas);
Paint paint = new Paint();
paint.setColor(Color.RED);
canvas.drawCircle(40, 40, 20, paint);
}
}//MainActivity
package com.mjl.gameView;import android.app.Activity;
import android.os.Bundle;public class MainActivity extends Activity {
/** Called when the activity is first created. */
GameView gameView = new GameView(MainActivity.this);
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(gameView);
}
}
package com.mjl.gameView;import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;public class GameView extends View{ Context context = null;
public GameView(Context context) {
super(context);
// TODO Auto-generated constructor stub
this.context=context;
}
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
super.onDraw(canvas);
Paint paint = new Paint();
paint.setColor(Color.RED);
canvas.drawCircle(40, 40, 20, paint);
}
}//MainActivity
package com.mjl.gameView;import android.app.Activity;
import android.os.Bundle;public class MainActivity extends Activity {
/** Called when the activity is first created. */
GameView gameView = new GameView(MainActivity.this);
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(gameView);
}
}
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要放到 onCreate里面
GameView gameView = new GameView(MainActivity.this);之所以这里不行,我想是因为new的时候,MainActivity还没初始化好,当然,这间接是由放的位置引起的,但java本身是允许放在楼主那个位置的。