使用 Intent 和 BroadcastReceiver 获取 Android 电池电量时的奇怪行为

Question

我试图在运行 Android 应用程序后找到电池电量。当手机启动应用程序并完全充电时，代码始终返回 100% 电池电量（即使电量已耗尽）。如果我以 75% 电量或其他电量启动应用程序，那么它会在测试结束时返回实际电池电量。我开始测试时，将手机插入计算机并保持电量，然后在执行应用程序之前拔掉它。理想情况下，我希望能够获得开始%和结束%，但两者的读取率也都是100%。所以这就是我正在做的事情...我从我的活动中称之为：

this.registerReceiver(this.mBatInfoReceiver, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));

然后在 BroadcastReceiver 中我做了很多事情（这需要一个多小时，因此电池电量会发生变化）。然后在BoradcastReceiver的末尾我调用它

int level2 = intent.getIntExtra("level", 0);    /* Ending battery level */
String end = "Ending battery level: " + String.valueOf(level2) + "%";

然后将String端发送到服务器。

我的代码如下所示：

package com.mdog.datareceive;

import java.io.IOException;
import java.io.PrintWriter;
import java.net.Socket;
import java.net.UnknownHostException;

import android.app.Activity;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.os.PowerManager;
import android.util.Log;
import android.widget.TextView;


public class Receive extends Activity {

    /* Test parameters */
    static int BYTES_TO_READ = 1024*1024*50;    /* The size of the data for each transfer */
    static int TIMES_TO_READ = 20;              /* The number of times the client will request the data */
    static int PLAYER_BUFFER_SIZE = 1638400;    /* Clients buffer size 1638400 = 1.57MB */
    static int SLEEP_TIME_MS = 5000;

    /* Display Info */
    String start = "empty";                 /* String holder for the starting battery life */
    String end = "empty2";                  /* String holder for the ending battery life */
    int allMBytes = 0;                      /* Integer holder for the total number of megabytes received during the test */
    TextView tv;                            /* The view the phone displays after completion of test */

    /* Server Info */
    String serverIP = "192.168.0.104";      /* Server IP */
    int serverPort = 11313;                 /* Server port number */



    private BroadcastReceiver mBatInfoReceiver = new BroadcastReceiver(){

        @Override
        public void onReceive(Context arg0, Intent intent) {

            //int level = intent.getIntExtra("level", 0);

            Socket connectionSocket = null;                         /* Socket to communicate with server */
            byte[] inputHolderByteArray = new byte[PLAYER_BUFFER_SIZE]; /* Used to read from the socket */

            int bufferBytes = 0;        /* filling the second buffer */
            int totalBytesRead = 0;     /* The total number of bytes read for this transfer round */
            int read=0;                 /* reading from stream, will contain the number of bytes read or -1 if the end has been hit */

            /* Acquire a wake lock for the phone so it does not go to sleep */
            PowerManager pm = (PowerManager) getSystemService(Context.POWER_SERVICE);
            PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.SCREEN_BRIGHT_WAKE_LOCK, getClass().getName());

            /* Connect to Server */
            try {

                connectionSocket = new Socket(serverIP, serverPort);
                connectionSocket.setReceiveBufferSize(PLAYER_BUFFER_SIZE); //1.5ish MB
                connectionSocket.setKeepAlive(true);
                PrintWriter out = new PrintWriter(connectionSocket.getOutputStream(), true);

                out.print("Client Info: Bytes expected per transfer:" + BYTES_TO_READ + ", Number of transfer to request:" + TIMES_TO_READ+ ", Buffer size:" +PLAYER_BUFFER_SIZE+ ", Sleep time(ms):" + SLEEP_TIME_MS + "\n");
                out.flush();

                wl.acquire();

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

                    out.print("Start\n");
                    out.flush();

                    while(totalBytesRead < BYTES_TO_READ){

                        /* Read at most PLAYER_BUFFER_SIZE bytes */
                        read = connectionSocket.getInputStream().read(inputHolderByteArray, 0, PLAYER_BUFFER_SIZE);

                        if(read != -1){
                            bufferBytes += read;
                            totalBytesRead  += read;
                            if(bufferBytes >= PLAYER_BUFFER_SIZE){
                                    try {
                                        Thread.sleep(SLEEP_TIME_MS);
                                    } catch (InterruptedException e) {
                                        e.printStackTrace();
                                    }
                                bufferBytes = 0;
                            }
                        }
                        else{
                            /* End of stream reached */
                            break;
                        }     
                    }

                    allMBytes += ((totalBytesRead/1024)/1024);
                    totalBytesRead = 0;

                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                }

                int level2 = intent.getIntExtra("level", 0);    /* Ending battery level */

                /* Put data on screen */
                start = "Starting battery level: 100%";
                end = "Ending battery level: " + String.valueOf(level2) + "%";
                out.print("Test Completed: " + start + ", " + end + ", Megabytes Read: " + allMBytes + "\n");
                out.flush();

                wl.release();

                tv.setText(start + "    \n" + end + "    \n Total MB transferred:" + allMBytes);
                setContentView(tv);

            } catch (UnknownHostException e) {
                Log.i("UnknownHost exception ", " ******************** Log Msg UHE " + e.getLocalizedMessage());
                e.printStackTrace();
            } catch (IOException e2) {
                Log.i("IO exception ", "******************** Log Msg IOE " + e2.toString());
                e2.printStackTrace();
            }
        }
    };


    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {

        tv = new TextView(this);                /* The view to post text to */
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        this.registerReceiver(this.mBatInfoReceiver, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
    }
}

Answer 1

首先，intent.getIntExtra("level", 0);不是百分比。 intent.getIntExtra(BatteryManager.EXTRA_LEVEL, 1) 需要与 intent.getIntExtra(BatteryManager.EXTRA_SCALE, 1) 进行比较才能获得百分比。

其次，不要在主应用程序线程上执行网络 I/O，例如 BroadcastReceiver 的 onReceive()。

第三，您正在将电池电量与自身进行比较。您需要等待下一个 ACTION_BATTERY_CHANGED 广播才能找到新的电池电量。

Answer 2

您不应该将应用程序逻辑放在 onReceive() 方法中。此方法应该只处理意图。否则，您可能会阻止向其他应用程序传递意图。

您的电池状态不会改变，因为您在此方法中阻塞时不会收到意图传递。传递的意图本身不会改变。只要电池状态发生变化，onReceive() 方法就会被调用——只要你不阻止它。