How to view continuous logcat in my Application in Emulator

问题

I am just getting the first 30 lines, how can I view the new lines being generated in my application, here is my code:

package com.example.showinlog;


public class ShowingLog extends Activity {

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        try {
            Process process = Runtime.getRuntime().exec("logcat");
            BufferedReader bufferedReader = new BufferedReader(
            new InputStreamReader(process.getInputStream()));

            StringBuilder log=new StringBuilder();
            String line; 
            while ((line = bufferedReader.readLine()) != null) {

              log.append(line);
              log.append("\n");

            }
            TextView tv = (TextView)findViewById(R.id.textView1);
            tv.setText(log.toString());
          } catch (IOException e) {
          }
    }
}

回答1:

I'm actually not sure how you get anything. The reading shouldn't ever "end", and since you don't do your reading in a different thread, you should never get to the part where you initialize the TextView.

Even if you did get to a point where you can continually log text, it wouldn't work with this code because you'd never be "done" building your StringBuilder.

Try this. You'll need to pass in a LogcatOut as a callback for the log data:

public class LolCat
{
    private Process proc;
    private LogcatOut logcatOut;

    public LolCat(LogcatOut logcatOut)
    {
        this.logcatOut = logcatOut;
    }

    private InputStream inStd;

    private InputStream inErr;

    private LogcatProcessStreamReader streamReader;
    private LogcatProcessStreamReader errStreamReader;

    public void start()
    {
        try
        {
            proc = Runtime.getRuntime().exec("logcat");
            OutputStream os = proc.getOutputStream();

            this.inStd = proc.getInputStream();
            this.inErr = proc.getErrorStream();

            startReaders();

            os.flush();
        }
        catch (IOException e)
        {
//            App.logExecption("Can't logcat", e);
        }
        catch (Exception e1)
        {
//            App.logExecption("Can't logcata", e1);
        }
    }

    private void startReaders() throws FileNotFoundException
    {
        this.streamReader = new LogcatProcessStreamReader(this.inStd, logcatOut);
        this.errStreamReader = new LogcatProcessStreamReader(this.inErr, null);

        streamReader.start();
        errStreamReader.start();
    }

    public void kill()
    {
        proc.destroy();
        if (this.streamReader != null)
            this.streamReader.finish();
        if (this.errStreamReader != null)
            this.errStreamReader.finish();
    }

    public abstract class LogcatOut
    {
        public abstract void writeLogData(byte[] data, int read) throws IOException;
        protected void cleanUp()
        {

        }
    }

    class LogcatProcessStreamReader extends Thread
    {
        private InputStream in;
        private boolean done = false;
        private LogcatOut logcatOut;

        public LogcatProcessStreamReader(InputStream in, LogcatOut logcatOut)
        {
            this.in = in;
            this.logcatOut = logcatOut;
        }

        @Override
        public void run()
        {
            byte[] b = new byte[8 * 1024];
            int read;

            try
            {
                while (!done && ((read = in.read(b)) != -1))
                {
                    if(logcatOut != null)
                        logcatOut.writeLogData(b, read);
                }

                if(logcatOut != null)
                    logcatOut.cleanUp();
            }
            catch (IOException e)
            {
//                App.logExecption("Can't stream", e);
            }
        }

        public synchronized void finish()
        {
            done = true;
        }
    }
}

In your onCreate:

    final Handler handler = new Handler();
    new LolCat(new LolCat.LogcatOut()
    {
        @Override
        public void writeLogData(final byte[] data, final int read) throws IOException
        {
            handler.post(new Runnable()
            {
                public void run()
                {
                    TextView tv = (TextView) asdf;
                    tv.setText(tv.getText() + "\n" + new String(data, 0, read));

                }
            });
        }
    });

A few caveats:

1) I adapted this from other code I have. I HAVE NOT tested it. You may hit a null pointer exception or the like, but the basic code should work.

2) You do need the log permission (forget what that is)

3) I don't remember if the log data comes from std out or err out. I think its std, but if you're getting nothing, swap.

4) I would not recommend concatting text like I did in here in a text view. You'll need to implement a buffer that can be limited, and large string concats are obviously bad in Java. I'll leave that solution to the reader...

回答2:

I found the AsyncTasks very useful when trying to implement this.

public class LogCatTask extends AsyncTask<Void, String, Void> {    
    public AtomicBoolean run = new AtomicBoolean(true);

    @Override
    protected Void doInBackground(Void... params) {
        try {
            Runtime.getRuntime().exec("logcat -c");
            Process process = Runtime.getRuntime().exec("logcat");
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(process.getInputStream()));
            StringBuilder log = new StringBuilder();
            String line = "";
            while (run.get()) {
                line = bufferedReader.readLine();
                if (line != null) {
                    log.append(line);
                    publishProgress(log.toString());
                }
                line = null;
                Thread.sleep(10);
            }
        }
        catch(Exception ex){

        }
        return null;
    }
}

And to implement the task you do something like

public void setupTextView(){
    textView.setMovementMethod(new ScrollingMovementMethod());
    logCatTask = new LogCatTask(){
        @Override
        protected void onProgressUpdate(String... values) {
            textView.setText(values[0]);
            super.onProgressUpdate(values);
        }
    };
    logCatTask.execute();
}

来源：https://stackoverflow.com/questions/8017082/how-to-view-continuous-logcat-in-my-application-in-emulator