Question

我的应用有一个启动活动

必须至少显示5秒

但是在这个活动中，我有另一个线程来同步来自互联网的数据

同步过程可能需要5秒以上或不到5秒。

如果少于5秒，处理程序应该等到第五秒

如果超过5秒，处理程序应该等到进程完成

如何让Handler等待另一个线程？

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    syncFromInternet(); // another thread may over 5 seconds

    new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
            Intent intent;
            intent = new Intent(getApplicationContext(), SecondActivity.class);
            startActivity(intent);
        }
    }, 5000);

}

Answer 1

您可以使用@Override protected void onCreate(Bundle savedInstanceState) { ... AsyncTask<Void, Void, Void> asyncTask = new AsyncTask<Void, Void, Void>() { private static final long FIVE_SECONDS = 5 * 1000; private volatile Date mStartTime; @Override protected void onPreExecute() { mStartTime = new Date(); } @Override protected Void doInBackground(Void... params) { // Do the syncing here syncFromInternet(); Date now = new Date(); long execTime = now.getTime() - mStartTime.getTime(); if(execTime < FIVE_SECONDS) { Thread.sleep(FIVE_SECONDS - execTime); } return null; } @Override protected void onPostExecute(Void result) { Intent intent = new Intent(...); startActivity(intent); finish(); } }; asyncTask.execute(null, null); }实例并测量与远程服务器同步的时间。如果时间大于5分钟，则开始新活动，否则 - 等到第5秒：

{{1}}

Answer 2

您可以使用此代码：

package com.example.untitled;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.os.Environment;
import android.os.Handler;
import android.os.Message;
import android.util.Log;

import java.io.File;
import java.io.IOException;

public class MyActivity extends Activity {

    private volatile boolean isAvailable = false;
    private volatile boolean isOver = false;

    private Handler messageHandler = new Handler() {
        public void handleMessage(Message msg) {
            super.handleMessage(msg);
            switch (msg.what) {
                case 0:
                    if (isOver) {
                        Log.e("messageHandler","isOver");
                        transitToNewActivity();
                    }else {
                        Log.e("messageHandler","isOver false");
                    }
                    break;
            }
        }
    };

    /**
     * Called when the activity is first created.
     */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        syncFromInternet(); // another thread may over 5 seconds

        new Handler().postDelayed(new Runnable() {
            @Override
            public void run() {
                isOver = true;
                Log.e("mainHandler", "Main handler expired");
                if (isAvailable) {
                    transitToNewActivity();
                    Log.e("mainHandler", "isAvailable");
                }else {
                    Log.e("mainHandler","isAvailable false");
                }
            }
        }, 50000);

    public void transitToNewActivity() {
        Log.e("transitToNewActivity","Activity transited");
        Intent intent;
        intent = new Intent(getApplicationContext(), SecondActivity.class);
        startActivity(intent);
    }

    public void syncFromInternet() {
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    Thread.sleep(80000);
                    isAvailable = true;
                    messageHandler.sendEmptyMessage(0);
                    Log.e("syncFromInternet", "internet data synced");
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        });
        thread.start();
    }
}

请根据您的要求进行修改。

Answer 3

你必须制作简单的逻辑，如

当处理程序完成时，检查syncFromInternet方法是否完成，如果它已完成打开主要活动

当syncFromInternet完成时，检查处理程序是否完成，如果它已完成打开主要活动。

代码中的上述说明：

boolean isHandlerCompleted = false, isAsyncCompleted = false;

new Handler().postDelayed(new Runnable() {
        @Override
        public void run() {
           isHandlerCompleted = true;
           if(isHandlerCompleted && isAsyncCompleted)
           {
           openMainActivity();// both thread completed 
           }
        }
    }, 5000);


// in your async task add this condition when it completes its task
isAsyncCompleted = true;
if(isHandlerCompleted && isAsyncCompleted)
{
openMainActivity();// both thread completed 
} // till this line

// make this function to open main activity
openMainActivity()
{
 Intent intent = new Intent(getApplicationContext(), SecondActivity.class);
 startActivity(intent);
}

Answer 4

执行线程后在syncFromInternet()内调用您的处理程序。

Answer 5

您应该实施AsyncTask，以便在syncFromInternet()完成之前等待。

    private class BackgroundSplashTask extends AsyncTask {

            @Override
            protected void onPreExecute() {
                super.onPreExecute();

               // show progressbar            

            }

            @Override
            protected Object doInBackground(Object[] params) {
                try {

                        syncFromInternet(); // sync in background
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }

                return null;
            }

            @Override
            protected void onPostExecute(Object o) {
                super.onPostExecute(o);
         // dismiss progressbar     
                Intent intent = new Intent(getApplicationContext(), SecondActivity.class);
                startActivity(intent);  // go to SecondActivity after syncFromInternet is completed
                finish();

            }

       }

让splash活动等待一个过程

5 个答案: