我一直收到与首选项有关的错误，我知道它已经贬值，所以我在这里寻求帮助 http://developer.android.com/reference/android/preference/PreferenceFragment.html
我完全按照底部所说的做了...
这里是错误:
12-04 00:39:37.553: E/AndroidRuntime(1164): FATAL EXCEPTION: main
12-04 00:39:37.553: E/AndroidRuntime(1164): Process: com.proteintracker, PID: 1164
12-04 00:39:37.553: E/AndroidRuntime(1164): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.proteintracker/com.proteintracker.MainPreferenceActivity}: java.lang.ClassCastException: com.proteintracker.MainPreferenceActivity cannot be cast to android.app.Activity
12-04 00:39:37.553: E/AndroidRuntime(1164): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2102)
12-04 00:39:37.553: E/AndroidRuntime(1164): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226)
12-04 00:39:37.553: E/AndroidRuntime(1164): at android.app.ActivityThread.access$700(ActivityThread.java:135)
12-04 00:39:37.553: E/AndroidRuntime(1164): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397)
12-04 00:39:37.553: E/AndroidRuntime(1164): at android.os.Handler.dispatchMessage(Handler.java:102)
12-04 00:39:37.553: E/AndroidRuntime(1164): at android.os.Looper.loop(Looper.java:137)
12-04 00:39:37.553: E/AndroidRuntime(1164): at android.app.ActivityThread.main(ActivityThread.java:4998)
12-04 00:39:37.553: E/AndroidRuntime(1164): at java.lang.reflect.Method.invokeNative(Native Method)
12-04 00:39:37.553: E/AndroidRuntime(1164): at java.lang.reflect.Method.invoke(Method.java:515)
12-04 00:39:37.553: E/AndroidRuntime(1164): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777)
12-04 00:39:37.553: E/AndroidRuntime(1164): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593)
12-04 00:39:37.553: E/AndroidRuntime(1164): at dalvik.system.NativeStart.main(Native Method)
12-04 00:39:37.553: E/AndroidRuntime(1164): Caused by: java.lang.ClassCastException: com.proteintracker.MainPreferenceActivity cannot be cast to android.app.Activity
12-04 00:39:37.553: E/AndroidRuntime(1164): at android.app.Instrumentation.newActivity(Instrumentation.java:1061)
12-04 00:39:37.553: E/AndroidRuntime(1164): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2093)
12-04 00:39:37.553: E/AndroidRuntime(1164): ... 11 more
这是我的 Preference 类的代码
package com.proteintracker;
import android.app.Activity;
import android.os.Bundle;
public class MainPreferenceActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Display the fragment as the main content.
getFragmentManager().beginTransaction()
.replace(android.R.id.content, new MainPreferenceFragment())
.commit();
}
}
这是我的偏好 fragment 类代码:
package com.proteintracker;
import android.os.Bundle;
import android.preference.PreferenceFragment;
public class MainPreferenceFragment extends PreferenceFragment {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Load the preferences from an XML resource
addPreferencesFromResource(R.xml.main_preferences);
}
}
这是我的 xml 文件
<?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" android:orderingFromXml="true">
<EditTextPreference
android:dialogMessage="Enter grams"
android:dialogTitle="Protein Grams"
android:key="gramsPerDay"
android:title="Grams per day" />
</PreferenceScreen>
这是 list 文件:
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.proteintracker"
android:versionCode="1"
android:versionName="1.0" >
<uses-sdk
android:minSdkVersion="11"
android:targetSdkVersion="18" />
<application
android:allowBackup="true"
android:icon="@drawable/ic_launcher"
android:label="@string/app_name"
>
<activity android:name="MainActivity"><intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter></activity><activity
android:name="MainPreferenceActivity"
android:label="@string/app_name" >
</activity>
<activity android:name="HelpActivity"></activity>
</application>
</manifest>
编辑---
这是我的主要 Activity 文件:
package com.proteintracker;
import android.app.Activity;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends Activity {
private OnClickListener buttonListener = new OnClickListener() {
@Override
public void onClick(View v) {
EditText editText = (EditText)findViewById(R.id.editText1);
Log.d("ProteinTracker", editText.getText().toString());
}
};
private OnClickListener helpButtonListener = new OnClickListener() {
@Override
public void onClick(View v) {
SharedPreferences preferences = getSharedPreferences("default", MODE_PRIVATE);
String value = preferences.getString("activityTest", "");
Log.d("ProteinTracker", value);
Intent intent = new Intent(MainActivity.this, MainPreferenceActivity.class);
startActivity(intent);
}
};
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if(savedInstanceState != null) {
Log.d("ProteinTracker", savedInstanceState.getString("keyName"));
}
TextView textView = (TextView) findViewById(R.id.mainActivityTextView);
textView.setText(R.string.test_updating_a_view);
Button button = (Button)findViewById(R.id.button1);
button.setOnClickListener(buttonListener );
Button helpButton = (Button)findViewById(R.id.helpButton);
helpButton.setOnClickListener(helpButtonListener );
SharedPreferences preferences = getSharedPreferences("default", MODE_PRIVATE);
Editor editor = preferences.edit();
editor.putString("activityTest", "activity value");
editor.commit();
}
@Override
protected void onSaveInstanceState(Bundle outState) {
outState.putString("keyName","string");
super.onSaveInstanceState(outState);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
MenuInflater menuInflater = getMenuInflater();
menuInflater.inflate(R.menu.main_menu, menu);
return true;
}
@Override
public boolean onOptionsItemSelected(MenuItem item) {
switch(item.getItemId()) {
case R.id.settingsMenuItem:
//launch settings activity
default:
}
return super.onOptionsItemSelected(item);
}
}
我更新了 fragment 文件并添加了一个新 fragment 文件，还包括了我的主要 Activity 文件。
我不确定我需要做什么，我是 Java 和 Android 的新手...谢谢!
最佳答案
fragment 需要添加到 Activity 中。您应该将 fragment 的名称从 MainPreferenceActivity 更改为 MainPreferenceFragment，这样您就可以:
public class MainPreferenceFragment extends PreferenceFragment {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Load the preferences from an XML resource
addPreferencesFromResource(R.xml.main_preferences);
}
}
然后让 MainPreferenceActivity 扩展 Activity，在其中添加 fragment :
public class MainPreference Activity extends Activity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// Display the fragment as the main content.
getFragmentManager().beginTransaction()
.replace(android.R.id.content, new MainPreferenceFragment())
.commit();
}
}
阅读更多 here .
关于java - Android - 应用程序不断因错误而崩溃 - 我认为这与首选项 fragment 有关，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/20367823/