我的应用程序总是在这个时候崩溃，请帮我解决这个问题。谢谢。
现在的情况如上面的标题所述。
这是我的 AndroidManifest.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright (C) 2009 The Android Open Source Project
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.android.contactmanager"
android:versionCode="1" android:versionName="1.0">
<uses-sdk android:minSdkVersion="10" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.MANAGE_ACCOUNTS"/>
<uses-permission android:name="android.permission.WRITE_OWNER_DATA"/>
<uses-permission android:name="android.permission.CAMERA"/>
<uses-permission android:name="android.permission.CALL_PHONE"/>
<uses-permission android:name="android.permission.GET_ACCOUNTS" />
<uses-permission android:name="android.permission.READ_CONTACTS" />
<uses-permission android:name="android.permission.WRITE_CONTACTS" />
<uses-permission android:name="android.permission.ACCESS_FINE_LOCATION"/>
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.CAMERA"/>
<uses-permission android:name="android.permission.ACCESS_COARSE_LOCATION"/>
<uses-permission android:name="android.permission.GET_ACCOUNTS"/>
<application android:label="@string/app_name" android:icon="@drawable/icon" android:allowBackup="true">
<!-- --><activity android:name=".ContactManager" android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<activity android:name="ContactAdder" android:label="@string/addContactTitle">
</activity>
<activity android:name=".SingleListContact"
android:label="Contact Person Details">
</activity>
</application>
</manifest>
SingleListContact.java
package com.example.android.contactmanager;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.widget.TextView;
public class SingleListContact extends Activity{
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
this.setContentView(R.layout.single_list_contact_view);
TextView txtContact = (TextView) findViewById(R.id.contactList);
Intent i = getIntent();
// getting attached intent data
String contact = i.getStringExtra("contact");
// displaying selected product name
txtContact.setText(contact);
}
}
我的 ContactManager.java 如下
/*
* Copyright (C) 2009 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.contactmanager;
import android.app.Activity;
import android.content.Intent;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.ContactsContract;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemClickListener;
import android.widget.Button;
import android.widget.CheckBox;
import android.widget.CompoundButton;
import android.widget.CompoundButton.OnCheckedChangeListener;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;
public final class ContactManager extends Activity implements OnItemClickListener
{
public static final String TAG = "ContactManager";
private Button mAddAccountButton;
private ListView mContactList;
private boolean mShowInvisible;
//public BooleanObservable ShowInvisible = new BooleanObservable(false);
private CheckBox mShowInvisibleControl;
/**
* Called when the activity is first created. Responsible for initializing the UI.
*/
@Override
public void onCreate(Bundle savedInstanceState)
{
Log.v(TAG, "Activity State: onCreate()");
super.onCreate(savedInstanceState);
setContentView(R.layout.contact_manager);
// Obtain handles to UI objects
mAddAccountButton = (Button) findViewById(R.id.addContactButton);
mContactList = (ListView) findViewById(R.id.contactList);
mShowInvisibleControl = (CheckBox) findViewById(R.id.showInvisible);
// Initialise class properties
mShowInvisible = false;
mShowInvisibleControl.setChecked(mShowInvisible);
// Register handler for UI elements
mAddAccountButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
Log.d(TAG, "mAddAccountButton clicked");
launchContactAdder();
}
});
mShowInvisibleControl.setOnCheckedChangeListener(new OnCheckedChangeListener()
{
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked)
{
Log.d(TAG, "mShowInvisibleControl changed: " + isChecked);
mShowInvisible = isChecked;
populateContactList();
}
});
mContactList = (ListView) findViewById(R.id.contactList);
mContactList.setOnItemClickListener(this);
// Populate the contact list
populateContactList();
}
/**
* Populate the contact list based on account currently selected in the account spinner.
*/
private void populateContactList() {
// Build adapter with contact entries
Cursor cursor = getContacts();
String[] fields = new String[] {
ContactsContract.Data.DISPLAY_NAME
};
SimpleCursorAdapter adapter = new SimpleCursorAdapter(this, R.layout.contact_entry, cursor,
fields, new int[] {R.id.contactEntryText});
mContactList.setAdapter(adapter);
}
/**
* Obtains the contact list for the currently selected account.
*
* @return A cursor for for accessing the contact list.
*/
private Cursor getContacts()
{
// Run query
Uri uri = ContactsContract.Contacts.CONTENT_URI;
String[] projection = new String[]
{
ContactsContract.Contacts._ID,
ContactsContract.Contacts.DISPLAY_NAME
};
String selection = ContactsContract.Contacts.IN_VISIBLE_GROUP + " = '" + (mShowInvisible ? "0" : "1") + "'";
//String selection = ContactsContract.Contacts.IN_VISIBLE_GROUP + " = '" + (mShowInvisible.get() ? "0" : "1") + "'";
String[] selectionArgs = null;
String sortOrder = ContactsContract.Contacts.DISPLAY_NAME + " COLLATE LOCALIZED ASC";
return this.managedQuery(uri, projection, selection, selectionArgs, sortOrder);
}
/**
* Launches the ContactAdder activity to add a new contact to the selected account.
*/
protected void launchContactAdder()
{
Intent i = new Intent(this, ContactAdder.class);
startActivity(i);
}
public void onItemClick(AdapterView<?> l, View v, int position, long id) {
Log.i("TAG", "You clicked item " + id + " at position " + position);
// Here you start the intent to show the contact details
// selected item
TextView tv=(TextView)v.findViewById(R.id.contactList);
String allcontactlist = tv.getText().toString();
// Launching new Activity on selecting single List Item
Intent i = new Intent(getApplicationContext(), SingleListContact.class);
// sending data to new activity
i.putExtra("Contact Person", allcontactlist);
startActivity(i);
}
}
联系人入口.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright (C) 2009 The Android Open Source Project
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="wrap_content"
android:layout_height="wrap_content">
<TextView android:text="@+id/contactEntryText"
android:id="@+id/contactEntryText"
android:layout_width="fill_parent"
android:textSize="30sp"
android:layout_height="wrap_content"/>
</LinearLayout>
联系人管理器.xml
<?xml version="1.0" encoding="utf-8"?>
<!-- Copyright (C) 2009 The Android Open Source Project
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical">
<ListView android:layout_width="wrap_content"
android:id="@+id/contactList"
android:layout_height="0dp"
android:padding="10dp"
android:textSize="200sp"
android:layout_weight="10"/>
<CheckBox android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:id="@+id/showInvisible"
android:text="@string/showInvisible"/>
<Button android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/addContactButton"
android:text="@string/addContactButtonLabel"/>
</LinearLayout>
日志猫结果：
12-05 05:00:31.289: E/AndroidRuntime(642): FATAL EXCEPTION: main
12-05 05:00:31.289: E/AndroidRuntime(642): java.lang.NullPointerException
12-05 05:00:31.289: E/AndroidRuntime(642): at com.example.android.contactmanager.ContactManager.onItemClick(ContactManager.java:148)
12-05 05:00:31.289: E/AndroidRuntime(642): at android.widget.AdapterView.performItemClick(AdapterView.java:284)
12-05 05:00:31.289: E/AndroidRuntime(642): at android.widget.ListView.performItemClick(ListView.java:3513)
12-05 05:00:31.289: E/AndroidRuntime(642): at android.widget.AbsListView$PerformClick.run(AbsListView.java:1812)
12-05 05:00:31.289: E/AndroidRuntime(642): at android.os.Handler.handleCallback(Handler.java:587)
12-05 05:00:31.289: E/AndroidRuntime(642): at android.os.Handler.dispatchMessage(Handler.java:92)
12-05 05:00:31.289: E/AndroidRuntime(642): at android.os.Looper.loop(Looper.java:123)
12-05 05:00:31.289: E/AndroidRuntime(642): at android.app.ActivityThread.main(ActivityThread.java:3683)
12-05 05:00:31.289: E/AndroidRuntime(642): at java.lang.reflect.Method.invokeNative(Native Method)
12-05 05:00:31.289: E/AndroidRuntime(642): at java.lang.reflect.Method.invoke(Method.java:507)
12-05 05:00:31.289: E/AndroidRuntime(642): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
12-05 05:00:31.289: E/AndroidRuntime(642): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
12-05 05:00:31.289: E/AndroidRuntime(642): at dalvik.system.NativeStart.main(Native Method)