Fragment之间共享一个Timer

最新推荐文章于 2022-08-24 07:28:06 发布

Luhuadeng

最新推荐文章于 2022-08-24 07:28:06 发布

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本文链接：https://blog.youkuaiyun.com/Luhuadeng/article/details/82832603

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本文介绍了一种在Android应用中，多个Fragment如何通过共享一个Timer实现周期性网络请求更新界面的方法。具体实现包括在MyApplication类中创建并提供Timer实例，各Fragment在onStart()方法中启动TimerTask，在onStop()方法中取消，确保资源合理利用。

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背景：

一个APP中有多个Activity构成，其中某些Activity中包含多个Fragment。并且这些Fragment都需要周期性的访问网络下载数据更新界面。比如Activity1中包含的Fragment1，Fragment2；Activity2中包含Fragment3，Fragment4。Fragment1每隔5秒访问网络并获取数据更新界面（比如获取天气信息），Fragment2每隔5秒访问网络获取路况信息；Fragment3每隔5秒获取停车场信息；Fragment4每隔5秒获取获取红绿灯信息。

Activit1 Fragment1 5秒获取天气信息
Fragment2 5秒获取路况信息
Activity2 Fragment3 5秒获取停车场信息
Fragment4 5秒获取红绿灯信息

实现方式：一个Timer，多个TimerTask的方式实现。
Step1：在MyApplication类中顶一个方法获取Timer对象；

Step2：每一个Fragment：在onStart（）方法中，向Timer对象添加定时周期任务TimerTask；在onStop（）方法中添加TimerTask定时任务的cancel方法结束定时周期任务。

Step3：在切换Activity时，清除当前Activity中所有的Fragment（从而调用当前Fragment中的onStop（）方法终止周期定时任务。）

MyApplication.java

public class MyApplication extends Application {
    private static Timer timer=null;
    public static Timer getTimer() {
        if(timer==null){
            timer = new Timer();
        }
        return timer;
    }
}

Manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.hnevc.multitimerdemo">

    <application
        android:name=".MyApplication"
        ……>
        <activity android:name=".MainActivity">
           ……
        </activity>
        <activity android:name=".Main2Activity"></activity>
    </application>

</manifest>

MainActivity.java

package com.hnevc.multitimerdemo;

import android.content.Intent;
import android.support.v4.app.Fragment;
import android.support.v4.app.FragmentManager;
import android.support.v4.app.FragmentTransaction;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.FrameLayout;

import java.util.Date;
import java.util.List;
import java.util.Timer;
import java.util.TimerTask;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = "MainActivity";
    private Timer timer;
    private BlankFragment1 fragment1;
    private BlankFragment2 fragment2;
    FrameLayout fl =null;
    FragmentManager fm;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        fm = getSupportFragmentManager();
        fragment1 = BlankFragment1.newInstance(null,null);
        fragment2 = BlankFragment2.newInstance(null,null);
        fl = findViewById(R.id.fl);
    }

    public void button1Click1(View view) {

            FragmentTransaction fragmentTransaction = fm.beginTransaction();
            fragmentTransaction.replace(R.id.fl,fragment1);
            fragmentTransaction.commit();
    }

    public void button2Click2(View view) {
            FragmentTransaction fragmentTransaction = fm.beginTransaction();
            fragmentTransaction.replace(R.id.fl,fragment2);
            fragmentTransaction.commit();
    }

    public void button3Click(View view) {
        List<Fragment> fragments = fm.getFragments();
        FragmentTransaction fragmentTransaction = fm.beginTransaction();
        for (int i = 0; i < fragments.size(); i++) {
            fragmentTransaction.remove(fragments.get(i));
        }
        fragmentTransaction.commit();
        Intent intent = new Intent(this, Main2Activity.class);
        startActivity(intent);
    }
}

Fragment1.java

package com.hnevc.multitimerdemo;

import android.content.Context;
import android.net.Uri;
import android.os.Bundle;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;

import java.util.Date;
import java.util.Timer;
import java.util.TimerTask;


public class BlankFragment1 extends Fragment {
    private static final String TAG = "BlankFragment1";
    
    private Timer timer;
    private TextView view;
    private TimerTask timerTask;

    public BlankFragment1() {
        // Required empty public constructor
    }
    // TODO: Rename and change types and number of parameters
    public static BlankFragment1 newInstance(String param1, String param2) {
        BlankFragment1 fragment = new BlankFragment1();
        return fragment;
    }

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        return inflater.inflate(R.layout.fragment_blank_fragment1, container, false);
        
    }
    
    @Override
    public void onStart() {
        super.onStart();
        timerTask = new TimerTask() {
            @Override
            public void run() {
                Log.e(TAG, "run: " + new Date().toString());
                getActivity().runOnUiThread(new Runnable() {
                    @Override
                    public void run() {
                        if(view==null){
                            view = getActivity().findViewById(R.id.tv_fragment);
                        }
                        view.setText(view.getText().toString() + "1");
                    }
                });

            }
        };
        timer = MyApplication.getTimer();
        Log.e(TAG, "onAttach: " );
        timer.schedule(timerTask, 1000,1000);
    }

    @Override
    public void onStop() {
        super.onStop();
        timerTask.cancel();
        Log.e(TAG, "onDetach: " );
    }
}

其他几个文件类似。