每当我单击手机上应用程序上的开始按钮时强制关闭？答案

【问题标题】：A Force Close whenever I click the start button on my app on my phone?每当我单击手机上应用程序上的开始按钮时强制关闭？
【发布时间】：2014-06-28 00:59:57
【问题描述】：

每次我点击我的 Android 应用程序中的开始按钮时，我都会强制关闭。我的代码中的错误为零，所以我很困惑为什么会这样。

fragment_main_menu.xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    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="com.app.whosesloganisthat.MainMenu$PlaceholderFragment" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <Button
        android:id="@+id/buttonStart"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView1"
        android:layout_below="@+id/textView1"
        android:layout_marginTop="37dp"
        android:text="@string/start"
        android:onClick="sendMessage" />


</RelativeLayout>

fragment_easy_level_info.xml：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    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="com.app.whosesloganisthat.EasyLevelInfo$PlaceholderFragment" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

</RelativeLayout>

MainMenu.java：

package com.app.whosesloganisthat;

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.EditText;
import android.os.Build;

public class MainMenu extends ActionBarActivity {
    public final static String EXTRA_MESSAGE = "com.app.whosesloganisthat.MESSAGE";

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

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }
    }

    @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, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /** Called when the user clicks the Send button */
    public void sendMessage(View view) {
        Intent intent = new Intent(this, EasyLevelInfo.class);
        EditText editText = (EditText) findViewById(R.id.container);
        String message = editText.getText().toString();
        intent.putExtra(EXTRA_MESSAGE, message);
        startActivity(intent);
        // Do something in response to button
    }
    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_main_menu,
                    container, false);
            return rootView;
        }
    }

}

EasyLevelInfo.java：

package com.app.whosesloganisthat;

import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.os.Build;

public class EasyLevelInfo extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_easy_level_info);
        Intent intent = getIntent();
        String message = intent.getStringExtra(MainMenu.EXTRA_MESSAGE);
        // Create the text view
        TextView textView = new TextView(this);
        textView.setTextSize(40);
        textView.setText(message);

        // Set the text view as the activity layout
        setContentView(textView);

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.easy_level_info, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();
        if (id == R.id.action_settings) {
            return true;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * A placeholder fragment containing a simple view.
     */
    public static class PlaceholderFragment extends Fragment {

        public PlaceholderFragment() {
        }

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            View rootView = inflater.inflate(R.layout.fragment_easy_level_info,
                    container, false);
            return rootView;
        }
    }

}

AndroidManifest.xml：

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

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="19" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.app.whosesloganisthat.MainMenu"
            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.app.whosesloganisthat.EasyLevelInfo"
            android:label="@string/title_activity_easy_level_info" >
        </activity>
        <activity
      android:name=".ToActivity"
      android:label="@string/app_name">    
      </activity>
    </application>

</manifest>

Logcat：

06-27 18:31:12.307: E/AndroidRuntime(16299): FATAL EXCEPTION: main
06-27 18:31:12.307: E/AndroidRuntime(16299): Process: com.app.whosesloganisthat, PID: 16299
06-27 18:31:12.307: E/AndroidRuntime(16299): java.lang.IllegalStateException: Could not execute method of the activity
06-27 18:31:12.307: E/AndroidRuntime(16299):    at android.view.View$1.onClick(View.java)
06-27 18:31:12.307: E/AndroidRuntime(16299):    at android.view.View.performClick(View.java)
06-27 18:31:12.307: E/AndroidRuntime(16299):    at android.view.View$PerformClick.run(View.java)
06-27 18:31:12.307: E/AndroidRuntime(16299):    at android.os.Handler.handleCallback(Handler.java)
06-27 18:31:12.307: E/AndroidRuntime(16299):    at android.os.Handler.dispatchMessage(Handler.java)
06-27 18:31:12.307: E/AndroidRuntime(16299):    at android.os.Looper.loop(Looper.java)
06-27 18:31:12.307: E/AndroidRuntime(16299):    at android.app.ActivityThread.main(ActivityThread.java)
06-27 18:31:12.307: E/AndroidRuntime(16299):    at java.lang.reflect.Method.invokeNative(Native Method)
06-27 18:31:12.307: E/AndroidRuntime(16299):    at java.lang.reflect.Method.invoke(Method.java:515)
06-27 18:31:12.307: E/AndroidRuntime(16299):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java)
06-27 18:31:12.307: E/AndroidRuntime(16299):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java)
06-27 18:31:12.307: E/AndroidRuntime(16299):    at dalvik.system.NativeStart.main(Native Method)
06-27 18:31:12.307: E/AndroidRuntime(16299): Caused by: java.lang.reflect.InvocationTargetException
06-27 18:31:12.307: E/AndroidRuntime(16299):    at java.lang.reflect.Method.invokeNative(Native Method)
06-27 18:31:12.307: E/AndroidRuntime(16299):    at java.lang.reflect.Method.invoke(Method.java:515)
06-27 18:31:12.307: E/AndroidRuntime(16299):    ... 12 more
06-27 18:31:12.307: E/AndroidRuntime(16299): Caused by: java.lang.NullPointerException
06-27 18:31:12.307: E/AndroidRuntime(16299):    at com.app.whosesloganisthat.MainMenu.sendMessage(MainMenu.java:51)
06-27 18:31:12.307: E/AndroidRuntime(16299):    ... 14 more

另外，如果您认为我忘记添加其他代码供您查看，请告诉我。非常感谢您的帮助！

【问题讨论】：

LogCat 说什么？据我所知，当应用程序像这样关闭时，LogCat 应该会提到一个错误。
它有帮助吗？
是的，它肯定有帮助。似乎您在方法sendMessage(View) 中有一个NullPointerException，可能在第51 行：EditText editText = (EditText) findViewById(R.id.container)，因为预计会膨胀的布局不是。但我看到@Hariharan 已经为您提供了答案。 ;-)

标签： java android eclipse forceclose

【解决方案1】：

试试这个..

从MainMenu 和EasyLevelInfo 中删除以下行

    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new PlaceholderFragment()).commit();
    }

还有MainMenu.java

改变这个

setContentView(R.layout.activity_main_menu);

到

setContentView(R.layout.fragment_main_menu);

因为Button onclick android:onClick="sendMessage" 只能在Activity 上工作

然后删除

setContentView(R.layout.activity_easy_level_info);

来自EasyLevelInfo.java，因为您正在以编程方式将 textview 设置为查看，所以不需要setContentView(textView);

编辑

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    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="com.app.whosesloganisthat.MainMenu$PlaceholderFragment" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

     <EditText
            android:id="@+id/container"
            android:layout_width="match_parent"
            android:layout_height="55dp" />

    <Button
        android:id="@+id/buttonStart"
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView1"
        android:layout_below="@+id/textView1"
        android:layout_marginTop="37dp"
        android:text="@string/start"
        android:onClick="sendMessage" />


</RelativeLayout>

【讨论】：

我现在可以打开应用程序了……但不幸的是，当我单击开始按钮时，应用程序强制关闭。
@shaanwarrior 容器在哪里 EditText 将其添加到fragment_main_menu.xml
我也删除了它......但是当我点击“开始”按钮时，我继续强制关闭。
我查看了 fragment_main_menu.xml，但没有容器 EditText。是否有必要让按钮正常工作？
@shaanwarrior 您正在从EditText 获取文本，那么您需要它。您是否在视图中输入任何文本？

【解决方案2】：

您在第 51 行的 sendMessage() 方法中抛出了一个 nullpointerexception，我假设它是以下行：

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

我认为可能发生的情况是，当您点击开始按钮时，它会查找 ID 为“容器”的editText，但找不到它。确保您的应用中确实有一个 ID 为“container”的editText。

【讨论】：

啊，我明白了。那我应该删除那行吗？
不，因为这会进一步破坏代码的其他部分。只需确保您已在其中一个 xml 文件中的某个位置实际定义了一个 editText ，其 id 为“container”。那应该修补一下。该代码本质上是在寻找一种叫做“容器”的东西，但没有找到它，然后抛出了一个空指针异常。