Question

我试图理解Null到底在说什么，但是它说有一个错误，我把一个数组的值设置正确。所以如果有人能给我一个解决方案会很棒。

logcat的：

02-29 23:03:52.078: D/Surface(4619): Surface is full screen
02-29 23:03:52.088: D/AndroidRuntime(4619): Shutting down VM
02-29 23:03:52.088: W/dalvikvm(4619): threadid=1: thread exiting with uncaught exception (group=0x4001d560)
02-29 23:03:52.088: E/AndroidRuntime(4619): FATAL EXCEPTION: main
02-29 23:03:52.088: E/AndroidRuntime(4619): java.lang.NullPointerException
02-29 23:03:52.088: E/AndroidRuntime(4619):     at com.ratetheplate.application.Reviews$Read.onProgressUpdate(Reviews.java:115)
02-29 23:03:52.088: E/AndroidRuntime(4619):     at com.ratetheplate.application.Reviews$Read.onProgressUpdate(Reviews.java:1)
02-29 23:03:52.088: E/AndroidRuntime(4619):     at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:432)
02-29 23:03:52.088: E/AndroidRuntime(4619):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-29 23:03:52.088: E/AndroidRuntime(4619):     at android.os.Looper.loop(Looper.java:130)
02-29 23:03:52.088: E/AndroidRuntime(4619):     at android.app.ActivityThread.main(ActivityThread.java:3835)
02-29 23:03:52.088: E/AndroidRuntime(4619):     at java.lang.reflect.Method.invokeNative(Native Method)
02-29 23:03:52.088: E/AndroidRuntime(4619):     at java.lang.reflect.Method.invoke(Method.java:507)
02-29 23:03:52.088: E/AndroidRuntime(4619):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:883)
02-29 23:03:52.088: E/AndroidRuntime(4619):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:641)
02-29 23:03:52.088: E/AndroidRuntime(4619):     at dalvik.system.NativeStart.main(Native Method)

爪哇：

package com.ratetheplate.application;

import java.io.IOException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.util.EntityUtils;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.Activity;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;
import android.widget.TextView;
import android.widget.Toast;

public class Reviews extends Activity {

TextView rssStuff;
HttpClient client;
JSONObject json;
final static String URL = "http://api.tumblr.com/v2/blog/ratetheplate.tumblr.com/posts.json?api_key=*********************";

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);

    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
            WindowManager.LayoutParams.FLAG_FULLSCREEN);

    setContentView(R.layout.reviews);
    rssStuff = (TextView) findViewById(R.id.rss);
    client = new DefaultHttpClient();
    new Read().execute("posts");

}

public JSONObject lastPost(String review) throws ClientProtocolException,
        IOException, JSONException {

    HttpGet get = new HttpGet(URL.toString());
    HttpResponse r = client.execute(get);
    int status = r.getStatusLine().getStatusCode();
    if (status == 200) {
        HttpEntity e = r.getEntity();
        String data = EntityUtils.toString(e);
        JSONArray timeline = new JSONArray(data);
        JSONObject last = timeline.getJSONObject(0);
        return last;
    } else {
        Toast.makeText(Reviews.this, "Error", Toast.LENGTH_SHORT);
        return null;
    }
}

public class Read extends AsyncTask<String, Integer, String> {

    String title, msg;
    ProgressDialog dialog;

    protected void onPreExectute() {
        title = "Loading";
        msg = "Loading Reviews...";
        dialog = new ProgressDialog(Reviews.this);
        dialog.setTitle(title);
        dialog.setMessage(msg);
        dialog.setIndeterminate(false);
        dialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
        dialog.setProgress(0);
        dialog.setMax(100);
        dialog.show();
        super.onPreExecute();
    }

    @Override
    protected String doInBackground(String... params) {
        // TODO Auto-generated method stub
        for (int i = 0; i < 20; i++) {
            publishProgress(5);
            try {
                Thread.sleep(88);
            } catch (InterruptedException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        dialog.dismiss();
        try {
            json = lastPost("posts");
            return json.getString(params[0]);
        } catch (ClientProtocolException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }

    protected void onProgressUpdate(Integer... progress) {
        dialog.incrementProgressBy(progress[0]);
        setProgress(progress[0]);
    }

    @Override
    protected void onPostExecute(String result) {
        // TODO Auto-generated method stub
        rssStuff.setText(result);
    }
}
}

Answer 1

您并未覆盖onPreExecute()的{{1}}方法。

您正在创建一个方法AsyncTask，您可以在其中对onPreExectute()进行初始化，但该方法既不是明确调用也不是dialog

因此AsyncTask dialog仍为null publishProgress

将拼写从onPreExectute()更改为onPreExecute()并在其上方添加@override。

Answer 2

也许您应该将ProgressDialog放在Main Activity中而不是AsyncTask中。然后在AsyncTask类中初始化它。我觉得这对我有用。希望这对你有用。

Answer 3

我在onPreExecute之前检查了你的项目并更改了初始化：

ProgressDialog dialog = new ProgressDialog(TestProjectActivity.this);

它对我有用。

onProgressUpdate的NullPointerException

3 个答案: