学步园

本文介绍在Android如何显示2D图像

1）使用XML，代码如下

 <ImageView<br /> android:layout_width="wrap_content"<br /> android:layout_height="wrap_content"<br /> android:src="@drawable/android"<br /> />

（代码比较简单，不做解析了！！）

2）继承View

根据public void setContentView (View view) ，新建一个继承View的类，并重写onDraw函数。代码如下：

package android.szu.edu.cn;</p> <p>import android.app.Activity;<br /> import android.content.Context;<br /> import android.graphics.Bitmap;<br /> import android.graphics.BitmapFactory;<br /> import android.graphics.Canvas;<br /> import android.graphics.Color;<br /> import android.os.Bundle;<br /> import android.view.View;<br /> import android.view.Window;</p> <p>public class Show2DImage extends Activity {<br /> /** Called when the activity is first created. */<br /> @Override<br /> public void onCreate(Bundle savedInstanceState) {<br /> super.onCreate(savedInstanceState);<br /> requestWindowFeature(Window.FEATURE_NO_TITLE);<br /> //setContentView(R.layout.main);<br /> setContentView(new Panel(this));<br /> }</p> <p> class Panel extends View{</p> <p> public Panel(Context context) {<br /> super(context);<br /> // TODO Auto-generated constructor stub<br /> }</p> <p> public void onDraw(Canvas canvas){<br /> Bitmap _scratch = BitmapFactory.decodeResource(getResources(), R.drawable.icon);<br /> canvas.drawColor(Color.BLACK);<br /> canvas.drawBitmap(_scratch, 10, 10, null);<br /> }<br /> }<br /> }

3）利用SurfaceView和Thread

package android.szu.edu.cn;</p> <p>import android.app.Activity;<br /> import android.content.Context;<br /> import android.graphics.Bitmap;<br /> import android.graphics.BitmapFactory;<br /> import android.graphics.Canvas;<br /> import android.graphics.Color;<br /> import android.os.Bundle;<br /> import android.view.SurfaceHolder;<br /> import android.view.SurfaceView;<br /> import android.view.Window;</p> <p>public class Show2DImage extends Activity {<br /> /** Called when the activity is first created. */<br /> @Override<br /> public void onCreate(Bundle savedInstanceState) {<br /> super.onCreate(savedInstanceState);<br /> requestWindowFeature(Window.FEATURE_NO_TITLE);<br /> // setContentView(R.layout.main);<br /> setContentView(new Panel(this));<br /> }</p> <p> // class Panel extends View{<br /> //<br /> // public Panel(Context context) {<br /> // super(context);<br /> // // TODO Auto-generated constructor stub<br /> // }<br /> //<br /> // public void onDraw(Canvas canvas){<br /> // Bitmap _scratch = BitmapFactory.decodeResource(getResources(),<br /> // R.drawable.icon);<br /> // canvas.drawColor(Color.BLACK);<br /> // canvas.drawBitmap(_scratch, 10, 10, null);<br /> // }<br /> // }</p> <p> class Panel extends SurfaceView implements SurfaceHolder.Callback {</p> <p> private Draw2DThread _thread;</p> <p> public Panel(Context context) {<br /> super(context);<br /> getHolder().addCallback(this);<br /> _thread = new Draw2DThread(getHolder(), this);<br /> }</p> <p> public void onDraw(Canvas canvas) {<br /> Bitmap _scratch = BitmapFactory.decodeResource(getResources(),<br /> R.drawable.android);<br /> canvas.drawColor(Color.BLACK);<br /> canvas.drawBitmap(_scratch, 10, 10, null);<br /> }</p> <p> @Override<br /> public void surfaceChanged(SurfaceHolder holder, int format, int width,<br /> int height) {<br /> // TODO Auto-generated method stub</p> <p> }</p> <p> @Override<br /> public void surfaceCreated(SurfaceHolder holder) {<br /> // TODO Auto-generated method stub<br /> _thread.setRunning(true);<br /> _thread.start();<br /> }</p> <p> @Override<br /> public void surfaceDestroyed(SurfaceHolder holder) {<br /> // TODO Auto-generated method stub<br /> boolean retry = true;<br /> _thread.setRunning(false);<br /> while (retry) {<br /> try {<br /> _thread.join();<br /> retry = false;<br /> } catch (InterruptedException e) {<br /> // TODO: handle exception<br /> }<br /> }<br /> }</p> <p> }</p> <p> class Draw2DThread extends Thread {<br /> private SurfaceHolder _surfaceHolder;<br /> private Panel _panel;<br /> private boolean _run;</p> <p> public Draw2DThread(SurfaceHolder surfaceHolder, Panel panel) {<br /> _surfaceHolder = surfaceHolder;<br /> _panel = panel;<br /> }</p> <p> public void setRunning(boolean run) {<br /> _run = run;<br /> }</p> <p> public void run() {<br /> Canvas c;<br /> while (_run) {<br /> c = null;<br /> try {<br /> c = _surfaceHolder.lockCanvas(null);<br /> synchronized (_surfaceHolder) {<br /> _panel.onDraw(c);<br /> }<br /> } finally {<br /> if (c != null) {<br /> _surfaceHolder.unlockCanvasAndPost(c);<br /> }<br /> }<br /> }</p> <p> }<br /> }<br /> }

第三种方法，可以快速地描绘界面，使用SurfaceView可以让其它非UI线程直接对画面进行操作。