异步任务——AsyncTask的初步认识

ProgressBar_test.class

package com.example.administrator.ten_9;

import android.app.Activity;

import android.os.AsyncTask;

import android.os.Bundle;

import android.util.Log;

import android.widget.ProgressBar;

import android.widget.TextView;

/**

 * Created by Administrator on 2015/10/9 0009.

 */

public class ProgressBar_test extends Activity {

    private ProgressBar progressBar;

    private my my;

    private TextView textView;

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.progressbar);

        progressBar = (ProgressBar) findViewById(R.id.pb);

        textView    = (TextView) findViewById(R.id.textjindu);

        my = new my();

        my.execute();

    }

    @Override

    protected void onPause() {

        super.onPause();

        //生命周期绑定

        //AsyncTask不为空而且是在Running的

        if (my != null && my.getStatus() == AsyncTask.Status.RUNNING){

            //cancel方法只是将对应的AsyncTask标记为cancel状态，并不是真正的取消线程执行。

            my.cancel(true);

        }

    }

    class my extends AsyncTask<Void,Integer,Void>{

        @Override

        protected Void doInBackground(Void... params) {

            //模拟进度更新

            for(int i = 0; i <= 100 ; i++){

                //判断是否被标记为 cancel 是 就break出来

                if(isCancelled()){

                    break;

                }

                publishProgress(i);

                try {

                    Thread.sleep(100);

                } catch (InterruptedException e) {

                    e.printStackTrace();

                }

            }

            return null;

        }

        @Override

        protected void onProgressUpdate(Integer... values) {

            super.onProgressUpdate(values);

            Log.d("xys", String.valueOf(values[0]));

            //判断是否被标记为 cancel 是 就直接返回

            if(isCancelled()){

                return;

            }

            //获取更新进度

            textView.setText(values[0]+"");

            progressBar.setProgress(values[0]);

        }

    }

}

　　

progressbar.xml

<?xml version="1.0" encoding="utf-8"?>

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:padding="16dp"

    android:layout_width="match_parent" android:layout_height="match_parent">

    <ProgressBar

        android:layout_centerInParent="true"

        style="?android:attr/progressBarStyleHorizontal"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:id="@+id/pb" />

    <TextView

        android:id="@+id/textjindu"

        android:gravity="center_horizontal"

        android:textSize="20sp"

        android:text="0"

        android:layout_below="@id/pb"

        android:layout_width="match_parent"

        android:layout_height="wrap_content" />

</RelativeLayout>

　　

MainActivity.class

public class MainActivity extends AppCompatActivity {

    @Override

    protected void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

        MyAsyncTask myAsyncTask = new MyAsyncTask();

        //start 异步处理myAsyncTask

        myAsyncTask.execute();

    }

    public void LoadImage(View view){

        startActivity(new Intent(this,ImageTest.class));

    }

    public void LoadProgress(View view){

        startActivity(new Intent(this,ProgressBar_test.class));

    }

}

　　mainactivity.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent"

    android:layout_height="match_parent" android:paddingLeft="@dimen/activity_horizontal_margin"

    android:paddingRight="@dimen/activity_horizontal_margin"

    android:paddingTop="@dimen/activity_vertical_margin"

    android:paddingBottom="@dimen/activity_vertical_margin" tools:context=".MainActivity">

    <Button

        android:id="@+id/bt1"

        android:text="跳转"

        android:onClick="LoadImage"

        android:layout_width="match_parent"

        android:layout_height="wrap_content" />

    <Button

        android:layout_below="@id/bt1"

        android:id="@+id/bt2"

        android:text="跳转2"

        android:onClick="LoadImage"

        android:layout_width="match_parent"

        android:layout_height="wrap_content" />

</RelativeLayout>