我想使用AsyncTask来管理我的应用程序中的一些业务逻辑.使用在separed文件中定义的AsyncTask的onProgressUpdate(…)方法的最佳模式是什么(而不是作为一个活动类别)
我有两个想法：
1.最简单的方法：在Activity中创建ProgressDialog(使用onCreateDialog(…)方法),并通过构造函数(在AsyncTask子类中覆盖onProgressUpdate(…))将引用传递给AsyncTask的子类.这个解决方案的缺点在于在业务逻辑代码中使用UI组件.
我有两个想法：
1.最简单的方法：在Activity中创建ProgressDialog(使用onCreateDialog(…)方法),并通过构造函数(在AsyncTask子类中覆盖onProgressUpdate(…))将引用传递给AsyncTask的子类.这个解决方案的缺点在于在业务逻辑代码中使用UI组件.
FooTask1.java：
public class FooTask1 extends AsyncTask<Void,Integer,Void> {
private ProgressDialog mProgressDialog;
public FooTask1(ProgressDialog progressDialog) {
super();
mProgressDialog = progressDialog;
}
@Override
protected Void doInBackground(Void... unused) {
// time consuming operation
for (int i=0; i<=100; i++) {
this.publishProgress(i);
try {
Thread.sleep(100);
} catch (Exception e) {}
}
return null;
}
@Override
protected void onProgressUpdate(Integer... progress) {
mProgressDialog.setProgress(progress[0]);
}
@Override
protected void onPostExecute(Void result) {
mProgressDialog.dismiss();
}
}
FooActivity1.java：
public class FooActivity1 extends Activity {
private static final int DIALOG_PROGRESS_ID = 0;
private ProgressDialog mProgressDialog;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
showDialog(DIALOG_PROGRESS_ID);
new FooTask(mProgressDialog).execute();
}
@Override
protected Dialog onCreateDialog(int id) {
switch(id) {
case DIALOG_PROGRESS_ID:
mProgressDialog = new ProgressDialog(this);
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mProgressDialog.setMessage("Loading...");
mProgressDialog.setCancelable(false);
return mProgressDialog;
default:
return null;
}
}
}
2.更复杂的方法：在Activity类中覆盖AsyncTask的onProgressUpdate(…)方法：
FooTask2.java：
public class FooTask2 extends AsyncTask<Void,Void> {
@Override
protected Void doInBackground(Void... unused) {
// time consuming operation
for (int i=0; i<=100; i++) {
this.publishProgress(i);
try {
Thread.sleep(100);
} catch (Exception e) {}
}
return null;
}
}
FooActivity2.java
public class FooActivity2 extends Activity {
private static final int DIALOG_PROGRESS_ID = 0;
private ProgressDialog mProgressDialog;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
showDialog(DIALOG_PROGRESS_ID);
new FooTaskLoader().execute();
}
@Override
protected Dialog onCreateDialog(int id) {
switch(id) {
case DIALOG_PROGRESS_ID:
mProgressDialog = new ProgressDialog(this);
mProgressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
mProgressDialog.setMessage("Loading...");
mProgressDialog.setCancelable(false);
return mProgressDialog;
default:
return null;
}
}
private class FooTaskLoader extends FooTask2 {
@Override
protected void onProgressUpdate(Integer... progress) {
mProgressDialog.setProgress(progress[0]);
}
@Override
protected void onPostExecute(Void result) {
dismissDialog(DIALOG_PROGRESS_ID);
}
}
}
解决方法
我宁愿从AsyncTask中隔离业务逻辑,而不是从Activity中分离AsyncTask.
一般来说,AsyncTask在Android应用程序生命周期中有一个非常具体的设计和用例,即在后台线程中运行一些耗时的任务,一旦完成,在UI线程中更新Activity的视图.这就是为什么总是推荐使用它作为一个内部的活动类.
更多的OO设计IMO将您的业务逻辑隔离并集中到POJO(为了可重用性).为了可测试性,您可以这样做：
1.定义界面IBusinessDAO
2.定义RealBusinessDAO实现IBusinessDAO
3.定义MockBusinessDAO实现IBusinessDAO
调用IBusinessDAO.foo();内部AsyncTask.doInBackground()
为了对您的业务逻辑进行单元测试,因为它是POJO,您可以使用纯JUnit编写测试用例.有时我们想测试UI组件,我们并不关心如何实现底层业务逻辑,例如,我的业务逻辑连接到远程http服务器下载一些json数据,我不想每次当我只是想测试UI布局,对于这种情况,我可以轻松地改变我的Activity使用MockBusinessDAO(Spring的DI概念),如下所示：
public class MyActivity extends Activity {
IBusinessDAO businessDAO;
... ...
private class MyAsyncTask extends AsyncTask<Void,Void,Void> {
... ...
protected void doInBackground(Void... params) {
businessDAO.foo();
}
}
... ...
public void onCreate(Bundle savedInstanceState) {
if (runInTest)
businessDAO = new MockBusinessDAO();
else
businessDAO = new RealBusinessDAO();
new myAsyncTask().execute();
}
}
做这些的一些优点是：
1. AsyncTask实现简单干净(doInBacnground()中的几行代码)
业务逻辑实现纯粹是POJO,提高可重用性.
3.隔离测试业务逻辑和UI组件,提高可测试性.
希望有帮助
