Android8.1 将crash信息保存到sdcard

背景：我做的是mtk平台，mtk本身有一个mtklogger可以保存日志，但是这个只在eng版本下会自动打开，user版本默认是关闭的，而且打开之后mtklogger有一个不可关闭的通知，这个看起来就很烦；
而且有一些发生crash的手机不能及时拿到，所以也无从分析问题所在，我的目标是将crash信息保存到手机中，然后在适当的时候上传的服务器，这样就可以远程分析问题了。

首先要在代码中找到crash信息，我通过crash的dialog最终找到了这个地方
framework/base/services/core/java/com/android/server/am/AppErrors.java
这个类看起来就感觉功能很明确，查看代码

void crashApplicationInner(ProcessRecord r, ApplicationErrorReport.CrashInfo crashInfo,
            int callingPid, int callingUid) {
        long timeMillis = System.currentTimeMillis();
        String shortMsg = crashInfo.exceptionClassName;
        String longMsg = crashInfo.exceptionMessage;
        String stackTrace = crashInfo.stackTrace;

        ......
    }

只看需要的部分，这里可以看到一个变量 stackTrace ，基本就可以确定是这个了，保险起见，打印log可以发现正是我所需要的crash信息。
现在的问题就是怎么把这个信息保存到手机sdcard中，在这里直接进行io读写，并不能成功。网上查了下，都说framework对文件进行读写操作比较麻烦，所以我就转移思路，把这个信息传递到apk模块内，在模块内在进行读写操作，我这里参考了IKeyguardService.aidl

新建framework/base/core/java/com/android/internal/policy/IErrorInfo.aidl

package com.android.internal.policy;


oneway interface IErrorInfo {

   void setError(String error);

}

新建framework/base/services/core/java/com/android/server/policy/ErrorInfoWrapper.java

package com.android.server.policy;

import android.content.Context;
import android.os.Bundle;
import android.os.IBinder;
import android.os.RemoteException;
import com.android.internal.policy.IErrorInfo;


public class ErrorInfoWrapper implements IErrorInfo {

    private IErrorInfo mService;

    public ErrorInfoWrapper(Context context, IErrorInfo service) {
        mService = service;
    }

    @Override
    public void setError(String error) {
        try {
            mService.setError(error);
        } catch (RemoteException e) {

        }
    }

    @Override // Binder interface
    public IBinder asBinder() {
        return mService.asBinder();
    }

}

新建framework/base/services/core/java/com/android/server/policy/ErrorInfoDelegate.java

package com.android.server.policy;

import android.app.ActivityManager;
import android.content.ComponentName;
import android.content.Context;
import android.content.Intent;
import android.content.ServiceConnection;
import android.os.Handler;
import com.android.internal.policy.IErrorInfo;
import com.android.server.UiThread;
import android.os.IBinder;
import android.os.UserHandle;

public class ErrorInfoDelegate {

    protected ErrorInfoWrapper mErrorInfoService;
    private final Context mContext;
    private final Handler mHandler;

    public ErrorInfoDelegate(Context context) {
        mContext = context;
        mHandler = UiThread.getHandler();
        bindService(context);
    }

    public void bindService(Context context) {
        Intent intent = new Intent();
        final ComponentName errorInfoComponent = ComponentName.unflattenFromString("com.android.systemui/com.android.systemui.keyguard.ErrorInfoService");
        intent.addFlags(Intent.FLAG_DEBUG_TRIAGED_MISSING);
        intent.setComponent(errorInfoComponent);

        context.bindServiceAsUser(intent, mErrorInfoConnection,
                Context.BIND_AUTO_CREATE, mHandler, UserHandle.SYSTEM);

    }

    private final ServiceConnection mErrorInfoConnection = new ServiceConnection() {
        @Override
        public void onServiceConnected(ComponentName name, IBinder service) {
            mErrorInfoService = new ErrorInfoWrapper(mContext,
                    IErrorInfo.Stub.asInterface(service));

        }

        @Override
        public void onServiceDisconnected(ComponentName name) {
            mErrorInfoService = null;

        }
    };

    public void setError(String error) {
        if (mErrorInfoService != null) {
            mErrorInfoService.setError(error);
        }
    }

}

在AppErrors.java中将crash信息传递到aidl中
services/core/java/com/android/server/am/AppErrors.java

private ErrorInfoDelegate mErrorInfoDelegate;

AppErrors(Context context, ActivityManagerService service) {
        context.assertRuntimeOverlayThemable();
        mService = service;
        mContext = context;
        /* begin */
        mService.mUiHandler.postDelayed(new Runnable() {
            @Override
            public void run() {
                mErrorInfoDelegate = new ErrorInfoDelegate(context);
            }
        }, 100000);
        /* end */
    }

void crashApplicationInner(ProcessRecord r, ApplicationErrorReport.CrashInfo crashInfo,
            int callingPid, int callingUid) {
        long timeMillis = System.currentTimeMillis();
        String shortMsg = crashInfo.exceptionClassName;
        String longMsg = crashInfo.exceptionMessage;
        String stackTrace = crashInfo.stackTrace;
        /* begin */
        if (mErrorInfoDelegate != null) {
            mErrorInfoDelegate.setError(shortMsg + longMsg + stackTrace);
        }
        /* end */
        if (shortMsg != null && longMsg != null) {
            longMsg = shortMsg + ": " + longMsg;
        } else if (shortMsg != null) {
            longMsg = shortMsg;
        }

        ......
}

这里实例化ErrorInfoDelegate的时候做了延时操作，主要怕影响到已有的逻辑。

到这里services中的操作已经完成，下面就是apk模块内的，我这里是在SystemUI中新增了一个service
AndroidManifest.xml中注册：

<service
                android:name=".keyguard.ErrorInfoService"
                android:exported="true"
                android:enabled="@bool/config_enableKeyguardService" />

新增ErrorInfoService.java

package com.android.systemui.keyguard;

import android.app.Service;
import android.content.Intent;
import android.os.*;
import com.android.internal.policy.IErrorInfo;
import com.android.systemui.util.LogUtil;

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

public class ErrorInfoService extends Service {

    @Override
    public void onCreate() {
    }

    @Override
    public IBinder onBind(Intent intent) {
        return mBinder;
    }

    private final IErrorInfo.Stub mBinder = new IErrorInfo.Stub() {

        @Override // Binder interface
        public void setError(String error) {
            writeText(error);
        }
    };

    private void writeText(String content) {

        if (content == null || content.equals("")) {
            return;
        }

        String filePath = "/storage/emulated/0/crashlog/";
        File dirFile = new File(filePath);
        if (!dirFile.exists()) {
            dirFile.mkdir();
        }
        String fileName = System.currentTimeMillis() + ".txt";
        File file = new File(filePath + fileName);
        FileOutputStream fos = null;
        try {
            fos = new FileOutputStream(file);
            fos.write(content.getBytes());
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if (fos != null) {
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }

    }

}

ok，这个时候如果有app发生了crash，那么在手机里就能保存这个crash信息了