(笔记)Android获取UncaughtException

    最近开发时应用出现崩溃，但是看不到当时的crash信息，没办法快速找到问题所在。后来在书中找到获取应用crash信息的方法，以此记录。

    crash发生时，系统会kill掉正在执行的程序，出现闪退或者提示用户程序已停止运行。开发人员也无法直接得知程序为何crash。Android提供了处理未捕获异常的方法。可以通过UncaughtExceptionHandler来监视应用的crash信息，给程序设置一个UncaughtExceptionHandler，当crash发生时，就会调用UncaughtExceptionHandler的uncaughtException方法，在uncaughtException方法里可以获取到异常信息，可以选择把异常信息存储。

import android.content.Context;
import android.os.Environment;
import android.os.Process;
import android.util.Log;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.PrintWriter;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * Created by Rewufu on 2016/2/17.
 */
public class CrachHandler implements Thread.UncaughtExceptionHandler {
    private static CrachHandler crachHandler = new CrachHandler();
    private Thread.UncaughtExceptionHandler uncaughtExceptionHandler;
    private Context mContext;
    private static final String PATH = Environment.getExternalStorageDirectory().getPath()+"/UncaughtException/";
    private static final String FILE_NAME = "crash";
    private static final String FILE_NAME_SUFFIX = ".trace";

    public static CrachHandler getInstance() {
        return crachHandler;
    }

    public void init(Context context) {
        uncaughtExceptionHandler = Thread.getDefaultUncaughtExceptionHandler();
        Thread.setDefaultUncaughtExceptionHandler(this);
        mContext = context;
    }

    @Override
    public void uncaughtException(Thread thread, Throwable ex) {

        try {
            dumpExceptionToSDcard(ex);
        } catch (IOException e) {
            e.printStackTrace();
        }

        if(uncaughtExceptionHandler != null){
            uncaughtExceptionHandler.uncaughtException(thread, ex);
        }else {
            Process.killProcess(Process.myPid());
        }

    }

    private void dumpExceptionToSDcard(Throwable ex) throws IOException{
        if(!Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
            Log.w("CrachHandler", "sdcard unmounted,skip dump exception");
            return;
        }

        File dir = new File(PATH);
        if(!dir.exists()){
            dir.mkdir();
        }
        long current = System.currentTimeMillis();
        String time = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(new Date(current));
        File file = new File(PATH + FILE_NAME + time + FILE_NAME_SUFFIX);
        PrintWriter printWriter = new PrintWriter(new BufferedWriter(new FileWriter(file)));
        printWriter.print(time);
        printWriter.println();
        ex.printStackTrace(printWriter);
        printWriter.close();
    }
}

     上面就是代码实现，首先实现一个UncaughtExceptionHandler对象，在它的uncaughtException方法获取异常信息并存储，调用Thread的setDefaultUncaughtExceptionHandler将它设置为线程默认的异常处理器。

    可以选择在Application初始化时为线程设置CrashHandler。

import android.app.Application;

/**
 * Created by Rewufu on 2016/2/17.
 */
public class Myapplication extends Application {
    @Override
    public void onCreate() {
        super.onCreate();
        CrachHandler crachHandler = CrachHandler.getInstance();
        crachHandler.init(getApplicationContext());
    }
}

     手动模拟发生crash，抛出一个RuntimeException测试一下，crash就会保存下来。

                throw new RuntimeException("自己抛出RuntimeException");