单例模式在android中的应用

项目演示及讲解

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项目下载
http://download.csdn.net/detail/u010134178/9052163
什么是单例模式

百度“java 单例”

以下是通过一个简单的列子来说明它的用户，别看这简单的例子，在公司项目里这可是最基本的呀

1、一个图片池类

public class ImagePool {

private static Context mContext;

private static Bitmap mBitmap;

private static ImagePool mInstance;

public ImagePool(Context context) {
mContext = context;
mBitmap = BitmapFactory.decodeStream(context.getResources()
.openRawResource(R.drawable.zheng));
}

public static ImagePool getInstance(Context context) {
if (null == mInstance) {
mInstance = new ImagePool(context);
}
return mInstance;
}

public static ImagePool getInstance() {
return mInstance;
}

/**
* 外部数据接口
*
* @return
*/
public Bitmap getBitmap() {
return mBitmap;
}

/**
* 设置
*
* @return
*/
public void setBitmap(int id) {
mBitmap = BitmapFactory.decodeStream(mContext.getResources()
.openRawResource(id));
}

}

一个Applaction层的全局变量

public class MyApplication extends Application{

@Override
public void onCreate() {
super.onCreate();
//init
ImagePool.getInstance(getApplicationContext());
}

}

在业务中的基本用法

public class MainActivity extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

final ImageView image = (ImageView) findViewById(R.id.imageId);
Button change = (Button) findViewById(R.id.changeId);
Button start = (Button) findViewById(R.id.startId);

Drawable drawable = new BitmapDrawable(ImagePool.getInstance()
.getBitmap());
image.setBackgroundDrawable(drawable);

change.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
ImagePool.getInstance().setBitmap(R.drawable.chuan);
Drawable drawable = new BitmapDrawable(ImagePool.getInstance()
.getBitmap());
image.setBackgroundDrawable(drawable);
}
});

start.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(MainActivity.this,
OtherActivity.class);
startActivity(intent);
}
});

}

}

好了，其实就这么简单。