android - 从主 Activity 切换到新 Activity 时应用程序崩溃

Question

当我使用菜单按钮切换到新页面并调用新 Activity 时，我的应用程序崩溃了。我遵循了 android 开发者网站的教程，该教程展示了如何将按钮点击链接到新 Activity ，但是当我点击按钮对象时，应用程序崩溃而没有更改为新 Activity 。

我有六个不同的 Activity 链接到主要 Activity 。

我的日志猫如下:

03-05 20:12:10.185: W/ActivityManager(288): Activity pause timeout for ActivityRecord{40d31ab0 u0 com.example.g00290342bvarley/.MainActivity}
03-05 20:12:10.394: E/SurfaceFlinger(36): ro.sf.lcd_density must be defined as a build property
03-05 20:12:10.954: E/SurfaceFlinger(36): ro.sf.lcd_density must be defined as a build property
03-05 20:12:11.065: W/EGL_emulation(863): eglSurfaceAttrib not implemented
03-05 20:12:11.474: I/QSB.SuggestionsProviderImpl(863): chars:0,corpora:[web, apps, com.android.contacts/.activities.PeopleActivity]
03-05 20:12:11.604: E/SurfaceFlinger(36): ro.sf.lcd_density must be defined as a build property
03-05 20:12:11.744: W/EGL_emulation(449): eglSurfaceAttrib not implemented
03-05 20:12:12.815: I/Choreographer(288): Skipped 32 frames!  The application may be doing too much work on its main thread.
03-05 20:12:13.114: D/dalvikvm(863): GC_CONCURRENT freed 398K, 13% free 3825K/4348K, paused 11ms+154ms, total 867ms
03-05 20:12:15.115: I/Process(1467): Sending signal. PID: 1467 SIG: 9
03-05 20:12:15.285: I/WindowState(288): WIN DEATH: Window{40dbdb70 u0 com.example.g00290342bvarley/com.example.g00290342bvarley.MainActivity}
03-05 20:12:15.297: I/ActivityManager(288): Process com.example.g00290342bvarley (pid 1467) has died.
03-05 20:12:15.455: W/InputMethodManagerService(288): Got RemoteException sending setActive(false) notification to pid 1467 uid 10048
03-05 20:12:36.119: D/ExchangeService(688): Received deviceId from Email app: null
03-05 20:12:36.119: D/ExchangeService(688): !!! deviceId unknown; stopping self and retrying
03-05 20:12:41.254: D/ExchangeService(688): !!! EAS ExchangeService, onCreate
03-05 20:12:41.264: D/ExchangeService(688): !!! EAS ExchangeService, onStartCommand, startingUp = false, running = false
03-05 20:12:41.284: W/ActivityManager(288): Unable to start service Intent { act=com.android.email.ACCOUNT_INTENT } U=0: not found
03-05 20:12:41.294: D/ExchangeService(688): !!! Email application not found; stopping self
03-05 20:12:41.304: D/ExchangeService(688): !!! EAS ExchangeService, onStartCommand, startingUp = true, running = false
03-05 20:12:41.334: W/ActivityManager(288): Unable to start service Intent { act=com.android.email.ACCOUNT_INTENT } U=0: not found
03-05 20:12:41.354: E/ActivityThread(688): Service com.android.exchange.ExchangeService has leaked ServiceConnection com.android.emailcommon.service.ServiceProxy$ProxyConnection@40d06b20 that was originally bound here

MainActivity 按钮方法所在的位置:

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.widget.EditText;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    //methods for button clicks

    public void aboutMeth(View view) {
        // Do something in response to button
        Intent intent = new Intent(this, AboutGmit.class);
        EditText editText = (EditText) findViewById(R.id.about);
        startActivity(intent);

    }

    public void mapMeth(View view) {
        // Do something in response to button
        Intent intent = new Intent(this, MapGmit.class);
        EditText editText = (EditText) findViewById(R.id.map);
        startActivity(intent);
    }

    public void courseMeth(View view) {
        // Do something in response to button
        Intent intent = new Intent(this, CourseInfo.class);
        EditText editText = (EditText) findViewById(R.id.courseInfo);
        startActivity(intent);
    }

    public void lifeMeth(View view) {
        // Do something in response to button
        Intent intent = new Intent(this, StudentLife.class);
        EditText editText = (EditText) findViewById(R.id.studLife);
        startActivity(intent);
    }


    public void portalMeth(View view) {
        // Do something in response to button
        Intent intent = new Intent(this, StudentPortal.class);
        EditText editText = (EditText) findViewById(R.id.studPortal);
        startActivity(intent);
    }

    public void contactMeth(View view) {
        // Do something in response to button
        Intent intent = new Intent(this, ContactInfo.class);
        EditText editText = (EditText) findViewById(R.id.contact);
        startActivity(intent);
    }

}

名为 ContactInfo.java 的新 Activity

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class ContactInfo extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_contact_info);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.contact_info, menu);
        return true;
    }

}

我在其中添加了 Activity 元素的 list 文件。

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.g00290342bvarley"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="17" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.example.g00290342bvarley.MainActivity"
            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="com.example.g00290342bvarley.AboutGmit"
            android:label="@string/title_activity_about_gmit" 
             android:parentActivityName="com.example.g00290342bvarley.MainActivity"
            >
        </activity>
        <activity
            android:name="com.example.g00290342bvarley.MapGmit"
            android:label="@string/title_activity_map_gmit"
             android:parentActivityName="com.example.g00290342bvarley.MainActivity"
            >
        </activity>
        <activity
            android:name="com.example.g00290342bvarley.CourseInfo"
            android:label="@string/title_activity_course_info" 
             android:parentActivityName="com.example.g00290342bvarley.MainActivity"
            >
        </activity>
        <activity
            android:name="com.example.g00290342bvarley.StudentLife"
            android:label="@string/title_activity_student_life" 
             android:parentActivityName="com.example.g00290342bvarley.MainActivity"
            >
        </activity>
        <activity
            android:name="com.example.g00290342bvarley.StudentPortal"
            android:label="@string/title_activity_student_portal" 
            android:parentActivityName="com.example.g00290342bvarley.MainActivity"
            >
        <meta-data
            android:name="android.support.PARENT_ACTIVITY"
            android:value="com.example.g00290342bvarley.MainActivity" />
        </activity>
        <activity
            android:name="com.example.g00290342bvarley.ContactInfo"
            android:label="@string/title_activity_contact_info" 
             android:parentActivityName="com.example.g00290342bvarley.MainActivity"
            >
        </activity>
    </application>

</manifest>

activity_main.xml 中的按钮布局

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout2"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/about"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:onClick="aboutMeth"
        android:hint="Details about GMIT"
        android:text="@string/about" />

    <Button
        android:id="@+id/map"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="95dp"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:onClick="mapMeth"
        android:hint="Location of GMIT on google maps"
        android:text="@string/map" />

    <Button
        android:id="@+id/courseInfo"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:onClick="courseMeth"
        android:hint="Info about courses offered by GMIT"
        android:text="@string/courseInfo" />

    <Button
        android:id="@+id/studLife"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="98dp"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:hint="Gallery"
        android:onClick="lifeMeth"
        android:text="@string/studLife" />

    <Button
        android:id="@+id/studPortal"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="93dp"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:onClick="portalMeth"
        android:hint="The Student Portal!"
        android:text="@string/studPortal" />

    <Button
        android:id="@+id/contact"
        style="?android:attr/buttonStyleSmall"
        android:layout_width="wrap_content"
        android:layout_height="0dp"
        android:layout_weight="1"
        android:onClick="contactMeth"
        android:hint="GMIT contact info"
        android:text="@string/contact" />

</LinearLayout>

Answer 1

我可能会遗漏一些东西，但我会试一试。在您尝试获取 editText 的每个 onClick 方法中。

EditText editText = (EditText) findViewById(R.id.contact);

但是你的layout里面没有声明editText，所以就变成了NullPointerException。尝试删除此行。希望对你有帮助