Question

我是Android图形的新手，就像自定义视图等。我有以下程序，但SurfaceView由于某种原因不会从另一个类的对象中绘制图像。我继续得到一个空指针异常。

主要课程：

public class Main extends Activity {

MyView view;
TestObject test;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    view = new MyView(this, this);
    test = new TestObject(this);
    setContentView(view);
}

public TestObject getTest() {
    return test;
}

public void setTest(TestObject test) {
    this.test = test;
}

}

查看课程：

public class MyView extends SurfaceView implements Runnable {


SurfaceHolder surfaceHolder;
Thread thread;
TestObject test;

public MyView(Context context, Main main) {
    super(context);
    this.test = main.getTest();
    surfaceHolder = getHolder();
    thread = new Thread(this);
    thread.start();
}

@Override
public void run() {
    while(true){
        if(!surfaceHolder.getSurface().isValid())
            continue;
        Canvas canvas = surfaceHolder.lockCanvas();
        canvas.drawBitmap(test.getImage(), test.getX(), test.getY(), null);
        surfaceHolder.unlockCanvasAndPost(canvas);
    }
}

}

对象类：

public class TestObject {

Main main;
Bitmap image;
int x,y;
DisplayMetrics dm;

public TestObject(Main main) {
    this.main = main;
    image = BitmapFactory.decodeResource(main.getResources(), R.drawable.ic_launcher);
    dm = new DisplayMetrics();
    x = dm.widthPixels / 2;
    y = dm.heightPixels / 2;
}

public Bitmap getImage() {
    return image;
}

public void setImage(Bitmap image) {
    this.image = image;
}

public int getX() {
    return x;
}

public void setX(int x) {
    this.x = x;
}

public int getY() {
    return y;
}

public void setY(int y) {
    this.y = y;
}   

}

我在MyView类的canvas.drawBitmap(test.getImage(), test.getX(), test.getY(), null);得到一个空指针异常。扼杀，如果要说canvas.drawBitmap(BitmapFactory.decodeResource(main.getResources(), R.drawable.ic_launcher), 0, 0, null);（或任何其他x，y位置），它将起作用。

任何帮助表示赞赏！

Answer 1

你应该覆盖＆＃34; onDraw＆＃34;方法＆＃34; MyView＆＃34;而不是实现Runnable。

如何从android中的另一个类中绘制图像？

1 个答案: