在除錯android app時，為了方便檢視logcat資訊，所以選擇把log資訊儲存在本地。在沒有wifi的情況下，無法選擇無線連線除錯，儲存log資訊到本地也是不錯的選擇。

程式碼如下:

importandroid.content.Context;
import android.os.Environment;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import 
 
java.io.InputStreamReader;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * Created by elena on 2017/9/4.
 */
public class LogcatHelper {

    private static LogcatHelper INSTANCE = null;
    private static String PATH_LOGCAT;
    private LogDumper mLogDumper = null;
    private int mPId
 
;

    /**
     *
     * 初始化目錄
     *
     * */
public void init(Context context) {
        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) {// 優先儲存到SD卡中
PATH_LOGCAT = Environment.getExternalStorageDirectory()
                    .getAbsolutePath() + File.separator 
 
+ "llvisionLog";
        } else {// 如果SD卡不存在，就儲存到本應用的目錄下
PATH_LOGCAT = context.getFilesDir().getAbsolutePath()
                    + File.separator + "llvisionLog";
        }
        File file = new File(PATH_LOGCAT);
        if (!file.exists()) {
            file.mkdirs();
        }

    }

    public static LogcatHelper getInstance(Context context) {
        if (INSTANCE == null) {
            INSTANCE = new LogcatHelper(context);
        }
        return INSTANCE;
    }

    private LogcatHelper(Context context) {
        init(context);
        mPId = android.os.Process.myPid();
    }

    public void start() {
        if (mLogDumper == null)
            mLogDumper = new LogDumper(String.valueOf(mPId), PATH_LOGCAT);
        mLogDumper.start();
    }

    public void stop() {
        if (mLogDumper != null) {
            mLogDumper.stopLogs();
            mLogDumper = null;
        }
    }

    private class LogDumper extends Thread {

        private Process logcatProc;
        private BufferedReader mReader = null;
        private boolean mRunning = true;
        String cmds = null;
        private String mPID;
        private FileOutputStream out = null;

        public LogDumper(String pid, String dir) {
            mPID = pid;
            try {
                out = new FileOutputStream(new File(dir, "log-"
+ getFileName() + ".log"));
            } catch (FileNotFoundException e) {
                // TODO Auto-generated catch block
e.printStackTrace();
            }

            /**
             *
             * 日誌等級：*:v , *:d , *:w , *:e , *:f , *:s
             *
             * 顯示當前mPID程式的 E和W等級的日誌.
             *
             * */
            // cmds = "logcat *:e *:w | grep \"(" + mPID + ")\"";
            // cmds = "logcat  | grep \"(" + mPID + ")\"";//列印所有日誌資訊
            // cmds = "logcat -s way";//列印標籤過濾資訊
cmds = "logcat *:e *:i | grep \"(" + mPID + ")\"";

        }

        public void stopLogs() {
            mRunning = false;
        }

        @Override
public void run() {
            try {
                logcatProc = Runtime.getRuntime().exec(cmds);
                mReader = new BufferedReader(new InputStreamReader(
                        logcatProc.getInputStream()), 1024);
                String line = null;
                while (mRunning && (line = mReader.readLine()) != null) {
                    if (!mRunning) {
                        break;
                    }
                    if (line.length() == 0) {
                        continue;
                    }
                    if (out != null && line.contains(mPID)) {
                        out.write((line + "\n").getBytes());
                    }
                }

            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (logcatProc != null) {
                    logcatProc.destroy();
                    logcatProc = null;
                }
                if (mReader != null) {
                    try {
                        mReader.close();
                        mReader = null;
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                if (out != null) {
                    try {
                        out.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                    out = null;
                }

            }

        }

    }
        public  String getFileName() {
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
            String date = format.format(new Date(System.currentTimeMillis()));
            return date;// 2012年10月03日 23:41:31
}

//        public  String getDateEN() {
//            SimpleDateFormat format1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
//            String date1 = format1.format(new Date(System.currentTimeMillis()));
//            return date1;// 2012-10-03 23:41:31
//        }
}

許可權：

1. <uses-permissionandroid:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
2. <uses-permissionandroid:name="android.permission.READ_LOGS"/>

1. publicclass MyApplication extends Application {  
2.     @Override
3.     publicvoid onCreate() {  
4.         // TODO Auto-generated method stub
5.         LogcatHelper.getInstance(this).start();  
6.     }  
7. }