Android SurfaceView未显示onDraw

问题描述

| 为了简单起见，我在SurfaceView上绘制一个整数，每次绘制都增加1。 正如我在System.out上看到的那样，实际上发生了增加。 屏幕上的文本停留在\'0 \'上。 谁能告诉我我做错了什么？ SurfaceViewTest.java

package com.niek.surfaceviewtest;

import android.app.Activity;
import android.os.Bundle;

public class SurfaceViewTest extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
    }
}

StatusView.java

package com.niek.surfaceviewtest;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.SurfaceHolder;
import android.view.SurfaceView;

public class StatusView extends SurfaceView implements SurfaceHolder.Callback {

    private int tmp;
    private DrawThread drawThread;

    public StatusView(Context context,AttributeSet attrs) {
        super(context,attrs);
        getHolder().addCallback(this);
        setFocusable(true);
        drawThread = new DrawThread(getHolder());
    }

    @Override
    public void onDraw(Canvas c) {
            c.drawColor(Color.BLACK);
        Paint p = new Paint();
        p.setColor(Color.RED);
        c.drawText(tmp + \"\",10,p);
        tmp++;

        System.out.println(tmp);
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder,int format,int width,int height) {
        // Todo Auto-generated method stub

    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        drawThread.setRunning(true);
        drawThread.start();
    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        // we have to tell thread to shut down & wait for it to finish,or else
        // it might touch the Surface after we return and explode
        boolean retry = true;
        drawThread.setRunning(false);
        while (retry) {
            try {
                drawThread.join();
                retry = false;
            } catch (InterruptedException e) {
                // we will try it again and again...
            }
        }
    }

    protected class DrawThread extends Thread {
        private SurfaceHolder surfaceHolder;
        private boolean isRunning;

        public DrawThread(SurfaceHolder surfaceHolder) {
            this.surfaceHolder = surfaceHolder;
            isRunning = false;
        }

        public void setRunning(boolean run) {
            isRunning = run;
        }

        public void run() {
            Canvas c;
            while (isRunning) {
                c = null;
                try {
                    c = surfaceHolder.lockCanvas(null);
                    synchronized (surfaceHolder) {
                        onDraw(c);
                    }
                } finally {
                    // do this in a finally so that if an exception is thrown
                    // during the above,we don\'t leave the Surface in an
                    // inconsistent state
                    if (c != null) {
                        surfaceHolder.unlockCanvasAndPost(c);
                    }
                }
            }
        }
    }
}

main.xml

<?xml version=\"1.0\" encoding=\"utf-8\"?>
<LinearLayout
    xmlns:android=\"http://schemas.android.com/apk/res/android\"
    android:layout_width=\"fill_parent\"
    android:layout_height=\"fill_parent\"
    android:background=\"#FFFFFF\">

    <com.niek.surfaceviewtest.StatusView
        android:id=\"@+id/statusview1\"
        android:layout_width=\"fill_parent\"
        android:layout_height=\"30dip\"
        android:background=\"#000000\"
 />
</LinearLayout>

    

解决方法

我唯一的猜测是，由于视图没有失效，因此未在表面上进行绘画。您应该调用

invalidate()

进行绘制，然后让框架调用

onDraw()

。也许这就是为什么增加“ 5”的原因，但是喷涂操作仅在第一次时到达表面。 可能值得尝试：也许让

Canvas c

成为

StatusView

的成员，然后替换

synchronized (surfaceHolder) {
  onDraw(c);
}

与

synchronized (surfaceHolder) {
  invalidate();
}

那样有用吗？     ,当前解决方案不正确。您正在使用ѭ10以便从单独的线程更新内容，而不是使用

invalidate()

方法，该方法将在系统刷新内容时运行

onDraw()

方法。问题是您为ѭ7设置了背景，请尝试删除该行

android:background=\"#000000\"

显然，您需要控制该视图中显示的全部信息。     ,看起来您正在使用setContentView（R.layout.main）显示main.xml；而不是创建表面并显示它。除非我在某处缺少代码，否则我认为情况并非如此。