android-code-程式異常處理與記錄log

這裡是分析的vlc的異常處理。

1，設定目前線程的異常處理函數

Thread.setDefaultUncaughtExceptionHandler(new VLCCrashHandler());      

2，在 VLCCrashHandler 中處理異常

public class VLCCrashHandler implements UncaughtExceptionHandler {

    private static final String TAG = "VLC/VlcCrashHandler";

    private UncaughtExceptionHandler defaultUEH;

    public VLCCrashHandler() {
        this.defaultUEH = Thread.getDefaultUncaughtExceptionHandler();
    }

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

        final Writer result = new StringWriter();
        final PrintWriter printWriter = new PrintWriter(result);

        // Inject some info about android version and the device, since google can't provide them in the developer console
        StackTraceElement[] trace = ex.getStackTrace();
        StackTraceElement[] trace2 = new StackTraceElement[trace.length+3];
        System.arraycopy(trace, 0, trace2, 0, trace.length);
        trace2[trace.length+0] = new StackTraceElement("Android", "MODEL", android.os.Build.MODEL, -1);
        trace2[trace.length+1] = new StackTraceElement("Android", "VERSION", android.os.Build.VERSION.RELEASE, -1);
        trace2[trace.length+2] = new StackTraceElement("Android", "FINGERPRINT", android.os.Build.FINGERPRINT, -1);
        ex.setStackTrace(trace2);

        ex.printStackTrace(printWriter);
        String stacktrace = result.toString();
        printWriter.close();
        Log.e(TAG, stacktrace);

        // Save the log on SD card if available
        if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {
            String sdcardPath = Environment.getExternalStorageDirectory().getPath();
            writeLog(stacktrace, sdcardPath + "/vlc_crash");//記錄日志
            writeLogcat(sdcardPath + "/vlc_logcat");//記錄日志
        }

        defaultUEH.uncaughtException(thread, ex);
    }

    private void writeLog(String log, String name) {
        CharSequence timestamp = DateFormat.format("yyyyMMdd_kkmmss", System.currentTimeMillis());
        String filename = name + "_" + timestamp + ".log";

        FileOutputStream stream;
        try {
            stream = new FileOutputStream(filename);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
            return;
        }

        OutputStreamWriter output = new OutputStreamWriter(stream);
        BufferedWriter bw = new BufferedWriter(output);

        try {
            bw.write(log);
            bw.newLine();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            try {
                bw.close();
                output.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private void writeLogcat(String name) {
        CharSequence timestamp = DateFormat.format("yyyyMMdd_kkmmss", System.currentTimeMillis());
        String filename = name + "_" + timestamp + ".log";
        try {
            Logcat.writeLogcat(filename);
        } catch (IOException e) {
            Log.e(TAG, "Cannot write logcat to disk");
        }
    }
}      

一個記錄的是崩潰的堆棧資訊，一個記錄的是崩潰時的logcat，結合使用，還是比較友善的。

下面是用到的Logcat類：

public class Logcat {
    public final static String TAG = "VLC/Util/Logcat";

    /**
     * Writes the current app logcat to a file.
     *
     * @param filename The filename to save it as
     * @throws IOException
     */
    public static void writeLogcat(String filename) throws IOException {
        String[] args = { "logcat", "-v", "time", "-d" };

        Process process = Runtime.getRuntime().exec(args);

        InputStreamReader input = new InputStreamReader(process.getInputStream());

        FileOutputStream fileStream;
        try {
            fileStream = new FileOutputStream(filename);
        } catch( FileNotFoundException e) {
            return;
        }

        OutputStreamWriter output = new OutputStreamWriter(fileStream);
        BufferedReader br = new BufferedReader(input);
        BufferedWriter bw = new BufferedWriter(output);

        try {
            String line;
            while ((line = br.readLine()) != null) {
                bw.write(line);
                bw.newLine();
            }
        }catch(Exception e) {}
        finally {
            bw.close();
            output.close();
            br.close();
            input.close();
        }
    }

    /**
     * Get the last 500 lines of the application logcat.
     *
     * @return the log string.
     * @throws IOException
     */
    public static String getLogcat() throws IOException {
        String[] args = { "logcat", "-v", "time", "-d", "-t", "500" };

        Process process = Runtime.getRuntime().exec(args);
        InputStreamReader input = new InputStreamReader(
                process.getInputStream());
        BufferedReader br = new BufferedReader(input);
        StringBuilder log = new StringBuilder();
        String line;

        while ((line = br.readLine()) != null)
            log.append(line + "\n");

        br.close();
        input.close();

        return log.toString();
    }

}