java - android.app.Application 无法转换 Yamba 应用程序？

Question

我的 Android 应用程序出现问题，当我在手机中测试它时，它立即崩溃，并收到此错误:

"java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.massine.final_pgm/com.example.massine.final_pgm.BaseActivity}: java.lang.ClassCastException: android.app.Application cannot be cast to com.example.massine.final_pgm.YambaApplication"

我不知道问题出在哪里，我读了类似的帖子，但我无法修复它:这是我的 java 类和我的 list :

<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.massine.final_pgm">


    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        <activity android:name="com.example.massine.final_pgm.BaseActivity"
            android:label="@string/app_name"
            android:theme="@style/AppTheme">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

<uses-permission android:name="android.permission.INTERNET" />
</manifest>

和我的java类:

package com.example.massine.final_pgm;

import android.app.Application;
import android.content.ContentValues;
import android.content.SharedPreferences;
import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
import android.preference.PreferenceManager;
import android.text.TextUtils;
import android.util.Log;
import java.util.List;

import winterwell.jtwitter.Twitter;
import winterwell.jtwitter.Twitter.Status;

public class YambaApplication extends Application implements OnSharedPreferenceChangeListener {
  private static final String TAG = YambaApplication.class.getSimpleName();
  public Twitter twitter; 
  private SharedPreferences prefs;
  private boolean serviceRunning;
  private StatusData statusData;


  @Override
  public void onCreate() {
    super.onCreate();
    this.prefs = PreferenceManager.getDefaultSharedPreferences(this);
    this.prefs.registerOnSharedPreferenceChangeListener(this);
    this.statusData = new StatusData(this);
    Log.i(TAG, "onCreated");
  }

  @Override
  public void onTerminate() {
    super.onTerminate();
    Log.i(TAG, "onTerminated");
  }

  // Returns the Twitter object
  public synchronized Twitter getTwitter() { 
    if (this.twitter == null) {
      String username = this.prefs.getString("username", null);
      String password = this.prefs.getString("password", null);
      String apiRoot = prefs.getString("apiRoot", "http://yamba.newcircle.com/api");
      if (!TextUtils.isEmpty(username) && !TextUtils.isEmpty(password)
          && !TextUtils.isEmpty(apiRoot)) {
        this.twitter = new Twitter(username, password);
        this.twitter.setAPIRootUrl(apiRoot);
      }
    }
    return this.twitter;
  }

  // Part of being OnSharedPreferenceChangeListener
  public synchronized void onSharedPreferenceChanged( 
      SharedPreferences sharedPreferences, String key) {
    this.twitter = null;
  }

  public boolean isServiceRunning() {
    return serviceRunning;
  }

  public void setServiceRunning(boolean serviceRunning) {
    this.serviceRunning = serviceRunning;
  }

  public StatusData getStatusData() {
    return statusData;
  }

  public SharedPreferences getPrefs() {
    return prefs;
  }

  // Connects to the online service and puts the latest statuses into DB.
  // Returns the count of new statuses
  public synchronized int fetchStatusUpdates() {
    Log.d(TAG, "Fetching status updates");
    Twitter twitter = this.getTwitter();
    if (twitter == null) {
      Log.d(TAG, "Twitter connection info not initialized");
      return 0;
    }
    try {
      List<Status> statusUpdates = twitter.getFriendsTimeline();
      long latestStatusCreatedAtTime = this.getStatusData()
          .getLatestStatusCreatedAtTime();
      int count = 0;
      ContentValues values = new ContentValues();
      for (Status status : statusUpdates) {
        values.put(StatusData.C_ID, status.getId());
        long createdAt = status.getCreatedAt().getTime();
        values.put(StatusData.C_CREATED_AT, createdAt);
        values.put(StatusData.C_TEXT, status.getText());
        values.put(StatusData.C_USER, status.getUser().getName());
        Log.d(TAG, "Got update with id " + status.getId() + ". Saving");
        this.getStatusData().insertOrIgnore(values);
        if (latestStatusCreatedAtTime < createdAt) {
          count++;
        }
      }
      Log.d(TAG, count > 0 ? "Got " + count + " status updates"
          : "No new status updates");
      return count;
    } catch (RuntimeException e) {
      Log.e(TAG, "Failed to fetch status updates", e);
      return 0;
    }
  }
}

问题所在行是:

yamba = ((YambaApplication) getApplication());

谢谢大家。

Answer 1

您需要在 list 文件中的应用程序元素上指定 android:name。

android:name="com.example.massine.final_pgm.YambaApplication"

如果没有它，代码会运行，但不会使用 YambaApplication 类，而是使用导致 ClassCastException 的默认应用程序。

根据评论进行编辑以进行澄清:

<application
    android:name="com.example.massine.final_pgm.YambaApplication"
    ...>