Android 2D图像显示

本文介绍在Android如何显示2D图像

1）使用XML，代码如下

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

（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;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.os.Bundle;
import android.view.View;
import android.view.Window;

public class Show2DImage extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
//setContentView(R.layout.main);
setContentView(new Panel(this));
}

class Panel extends View{

public Panel(Context context) {
super(context);
// TODO Auto-generated constructor stub
}

public void onDraw(Canvas canvas){
Bitmap _scratch = BitmapFactory.decodeResource(getResources(), R.drawable.icon);
canvas.drawColor(Color.BLACK);
canvas.drawBitmap(_scratch, 10, 10, null);
}
}
}

3）利用SurfaceView和Thread

package android.szu.edu.cn;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.os.Bundle;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.Window;

public class Show2DImage extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
// setContentView(R.layout.main);
setContentView(new Panel(this));
}

// class Panel extends View{
//
// public Panel(Context context) {
// super(context);
// // TODO Auto-generated constructor stub
// }
//
// public void onDraw(Canvas canvas){
// Bitmap _scratch = BitmapFactory.decodeResource(getResources(),
// R.drawable.icon);
// canvas.drawColor(Color.BLACK);
// canvas.drawBitmap(_scratch, 10, 10, null);
// }
// }

class Panel extends SurfaceView implements SurfaceHolder.Callback {

private Draw2DThread _thread;

public Panel(Context context) {
super(context);
getHolder().addCallback(this);
_thread = new Draw2DThread(getHolder(), this);
}

public void onDraw(Canvas canvas) {
Bitmap _scratch = BitmapFactory.decodeResource(getResources(),
R.drawable.android);
canvas.drawColor(Color.BLACK);
canvas.drawBitmap(_scratch, 10, 10, null);
}

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

}

@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
_thread.setRunning(true);
_thread.start();
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
boolean retry = true;
_thread.setRunning(false);
while (retry) {
try {
_thread.join();
retry = false;
} catch (InterruptedException e) {
// TODO: handle exception
}
}
}

}

class Draw2DThread extends Thread {
private SurfaceHolder _surfaceHolder;
private Panel _panel;
private boolean _run;

public Draw2DThread(SurfaceHolder surfaceHolder, Panel panel) {
_surfaceHolder = surfaceHolder;
_panel = panel;
}

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

public void run() {
Canvas c;
while (_run) {
c = null;
try {
c = _surfaceHolder.lockCanvas(null);
synchronized (_surfaceHolder) {
_panel.onDraw(c);
}
} finally {
if (c != null) {
_surfaceHolder.unlockCanvasAndPost(c);
}
}
}

}
}
}

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。