【移动应用开发技术】android中AsyncTask类的示例分析

【移动应用开发技术】android中AsyncTask类的示例分析

AsyncTask类的声明：Result执行异步任务后，需要返回的结果的数据类型

publicfinalAsyncTask<params,Progress,Result>execute(params...params)<Button

android:id="@+id/button1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentTop="true"

android:layout_centerHorizontal="true"

android:layout_marginTop="104dp"

android:onClick="doAsyncTask"

android:text="开始"

/>MainActivity：

public

class

MainActivity

extends

Activity

{

@Override

protected

void

onCreate(Bundle

savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

System.out.println("onCreate"

+

Thread.currentThread().getId());

}

public

void

doAsyncTask(View

view){

new

InnerAsyncTask().execute("");

}

private

class

InnerAsyncTask

extends

AsyncTask<Object,

Object,

Object>{

@Override

protected

Object

doInBackground(Object...

params)

{

for(int

i

=

0;

i

<

30;i++){

System.out.println("InnerAsyncTask"

+

Thread.currentThread().getId());

try

{

Thread.sleep(1000);

}

catch

(InterruptedException

e)

{

e.printStackTrace();

}

}

return

null;

}

}

}AsyncTask更新UIprotectedvoidonPostExecute(Resultresult)<Button

android:id="@+id/button1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentTop="true"

android:layout_centerHorizontal="true"

android:layout_marginTop="104dp"

android:onClick="doAsyncTask"

android:text="开始"

/>

<ImageView

android:id="@+id/imageView1"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_below="@+id/button1"

android:layout_centerHorizontal="true"

android:layout_marginTop="22dp"

android:src="@drawable/abs"

/>MainActivity：

public

class

MainActivity

extends

Activity

{

private

ImageView

image;

@Override

protected

void

onCreate(Bundle

savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

image

=

(ImageView)

findViewById(R.id.imageView1);

//

System.out.println("onCreate"

+

Thread.currentThread().getId());

}

public

void

doAsyncTask(View

view){

new

InnerAsyncTask().execute("");

}

private

class

InnerAsyncTask

extends

AsyncTask<String,Integer,

Bitmap>{

@Override

protected

Bitmap

doInBackground(String...

params)

{

try

{

Thread.sleep(3000);

}

catch

(InterruptedException

e)

{

//

TODO

Auto-generated

catch

block

e.printStackTrace();

}

return

BitmapFactory.decodeResource(getResources(),

R.drawable.abc);

}

@Override

protected

void

onPostExecute(Bitmap

result)

{

image.setImageBitmap(result);

}

}

}

AsyncTask更新进度

<RelativeLayout

xmlns:android="/apk/res/android"

xmlns:tools="/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

>

<TextView

android:id="@+id/tv_pb"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:text="100%"

android:visibility="gone"

android:textSize="16sp"/>

<Button

android:id="@+id/btn_update"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentTop="true"

android:layout_centerHorizontal="true"

android:layout_marginTop="104dp"

android:onClick="doAsyncTask"

android:text="开始"

/>

<ImageView

android:id="@+id/iv_image"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_below="@+id/btn_update"

android:layout_centerHorizontal="true"

android:layout_marginTop="22dp"

android:src="@drawable/abs"

/>

<ProgressBar

android:id="@+id/pb_progress"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:layout_alignParentTop="true"

android:max="100"

android:visibility="gone"

android:layout_alignRight="@+id/btn_update"

android:layout_marginTop="32dp"

/>

</RelativeLayout>LoadImage：public

class

LoadImage

extends

AsyncTask<String,

Integer,

Object>

{

private

Context

context;

private

ImageView

imageview;

private

Bitmap

image;

private

Button

button;

private

ProgressBar

pg;

private

TextView

tv;

public

LoadImage(Context

context,

Button

button,

ImageView

imageview,

ProgressBar

pg,

TextView

tv)

{

this.context

=

context;

this.imageview

=

imageview;

this.button

=

button;

this.pg

=

pg;

this.tv

=

tv;

}

@Override

protected

Object

doInBackground(String...

params)

{

for

(int

i

=

0;

i

<=

100;

i++)

{

publishProgress(i);

try

{

Thread.sleep(50);

}

catch

(InterruptedException

e)

{

//

TODO

Auto-generated

catch

block

e.printStackTrace();

}

}

image

=

BitmapFactory.decodeResource(context.getResources(),

R.drawable.abc);

return

null;

}

@Override

protected

void

onProgressUpdate(Integer...

values)

{

//

TODO

Auto-generated

method

stub

pg.setProgress(values[0]);

tv.setText(values[0]

+

"%");

}

@Override

protected

void

onPostExecute(Object

result)

{

imageview.setImageBitmap(image);

button.setEnabled(true);

pg.setVisibility(View.GONE);

tv.setVisibility(View.GONE);

}

}MainActivity：

public

class

MainActivity

extends

Activity

{

private

ImageView

image;

private

Button

button;

private

ProgressBar

pg;

private