Android_AsyncTask异步任务 _asynctask

当筵意气临九霄，星离雨散不终朝。这篇文章主要讲述Android_AsyncTask异步任务相关的知识，希望能为你提供帮助。
AsyncTask,是android提供的轻量级的异步类,可以直接继承AsyncTask,在类中实现异步操作,并提供接口反馈当前异步执行的程度(可以通过接口实现UI进度更新),最后反馈执行的结果给UI主线程
好了，我们就看看效果
activity_main.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:paddingBottom="@dimen/activity_vertical_margin" android:paddingLeft="@dimen/activity_horizontal_margin" android:paddingRight="@dimen/activity_horizontal_margin" android:paddingTop="@dimen/activity_vertical_margin" tools:context="com.example.multithreadind01.MainActivity" > < TextView android:id="@+id/textView1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:text="@string/hello_world" /> < Button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentRight="true" android:layout_alignTop="@+id/textView1" android:layout_marginRight="53dp" android:text="Button" /> < ListView android:id="@+id/listView1" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_below="@+id/button1" android:layout_marginTop="84dp" > < /ListView> < !-- 进度条 --> < ProgressBar android:id="@+id/progressBar1" style="?android:attr/progressBarStyleHorizontal" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignLeft="@+id/listView1" android:layout_alignRight="@+id/button1" android:layout_below="@+id/button1" android:layout_marginTop="28dp" /> < /RelativeLayout>

效果图:

文章图片

item.xml

< ?xml version="1.0" encoding="utf-8"?> < LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="horizontal" > < TextView android:id="@+id/username" android:layout_weight="1" android:layout_width="match_parent" android:layout_height="60dp" android:textSize="45dp"
android:text="1" /> < TextView android:id="@+id/sex" android:layout_weight="1" android:layout_width="match_parent" android:layout_height="60dp" android:textSize="45dp"
android:text="2" /> < /LinearLayout>

效果图:

文章图片

java代码： User实体类

package com.example.multithreadind01; public class User { private String username; private String sex; public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; }}

MainActivity.java

package com.example.asynctask; import java.util.ArrayList; import java.util.List; import android.app.Activity; import android.os.Bundle; import android.util.Log; import android.view.LayoutInflater; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.view.View.OnClickListener; import android.widget.BaseAdapter; import android.widget.Button; import android.widget.ListView; import android.widget.TextView; public class MainActivity extends Activity { private TextView tv1; //item.xml里的TextView：Textviewname private TextView tv2; //item.xml里的TextView：Textviewage private Button bt; //activity_main.xml里的Button private ListView lv; //activity_main.xml里的ListView private BaseAdapter adapter; //要实现的类 private List< User> userList = new ArrayList< User> (); //实体类 @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); bt = (Button) findViewById(R.id.Button); lv = (ListView) findViewById(R.id.listView1); //模拟数据库 for (int i = 0; i < 5; i++) { User ue = new User(); //给实体类赋值 ue.setName("小米"+i); ue.setAge("18"); userList.add(ue); }bt.setOnClickListener(new OnClickListener() {@Override public void onClick(View v) { MyTask mt = new MyTask(MainActivity.this); mt.execute(userList,adapter); //里面的参数是传给doInBackground} }); adapter = new BaseAdapter() { @Override public int getCount() { // TODO Auto-generated method stub return userList.size(); //数目 }@Override public View getView(int position, View convertView, ViewGroup parent) { LayoutInflater inflater = MainActivity.this.getLayoutInflater(); View view; if (convertView==null) { //因为getView()返回的对象，adapter会自动赋给ListView view = inflater.inflate(R.layout.item, null); }else{ view=convertView; Log.i("info","有缓存，不需要重新生成"+position); } tv1 = (TextView) view.findViewById(R.id.Textviewname); //找到Textviewname tv1.setText(userList.get(position).getName()); //设置参数tv2 = (TextView) view.findViewById(R.id.Textviewage); //找到Textviewage tv2.setText(userList.get(position).getAge()); //设置参数 return view; } @Override public long getItemId(int position) {//取在列表中与指定索引对应的行id return 0; } @Override public Object getItem(int position) {//获取数据集中与指定索引对应的数据项 return null; } }; lv.setAdapter(adapter); }}

MyTask.java //也是继承AsyncTask这个重点的类

package com.example.asynctask; import java.util.List; import android.os.AsyncTask; import android.util.Log; import android.widget.BaseAdapter; import android.widget.ProgressBar; import android.widget.TextView; import android.widget.Toast; public class MyTask extends AsyncTask{ private MainActivity activity; private BaseAdapter adapter; private List< User> userList; public MyTask(MainActivity activity){ this.activity = activity; } @Override protected Object doInBackground(Object... params) { userList = (List< User> ) params[0]; adapter = (BaseAdapter) params[1]; for (int i = 0; i < userList.size(); i++) { //模拟网络 try { Thread.sleep(1000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); }userList.get(i).setName("小红"+i); //模拟网络悄悄的更改name userList.get(i).setAge("2"+i); publishProgress(i); } return "你好"; } //准备 @Override protected void onPreExecute() { Toast.makeText(activity, "开始中", Toast.LENGTH_SHORT).show(); } //做完后执行 @Override protected void onPostExecute(Object result) { String r = result.toString(); //得到返回值 TextView tv = (TextView)activity.findViewById(R.id.textView1); tv.setText(r+"访问完成！"); } //分步完成 @Override protected void onProgressUpdate(Object... values) {int bar = Integer.parseInt(values[0].toString()); bar = (bar+1)*20; ProgressBar progressBar = (ProgressBar)activity.findViewById(R.id.ProgressBar); //进度条 progressBar.setProgress(bar); adapter.notifyDataSetChanged(); }}

打开效果图: