Question

尝试创建一个应用程序，我正在尝试创建一个简单的转换器。当我运行模拟器时，应用程序很快崩溃，所以我不确定它为什么会崩溃。我允许我运行模拟器

以下是我在logcat中看到的内容：

07-09 20:28:10.220  17354-17354/com.example.adrew.convertmidterm         E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.adrew.convertmidterm, PID: 17354
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.adrew.convertmidterm/com.example.adrew.convertmidterm.MainActivity}: android.view.InflateException: Binary XML file line #1: Error inflating class fragment
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
        at android.app.ActivityThread.access$800(ActivityThread.java:151)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5257)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
 Caused by: android.view.InflateException: Binary XML file line #1: Error inflating class fragment
        at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:763)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:482)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
        at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
        at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:378)
        at android.app.Activity.setContentView(Activity.java:2145)
        at com.example.adrew.convertmidterm.MainActivity.onCreate(MainActivity.java:14)
        at android.app.Activity.performCreate(Activity.java:5990)
        at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)


      at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
    at android.app.ActivityThread.access$800(ActivityThread.java:151)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.view.View android.view.View.findViewById(int)' on a null object reference at com.example.adrew.convertmidterm.MainActivityFragment.onCreateView(MainActivityFragment.java:33)
            at android.app.Fragment.performCreateView(Fragment.java:2053)
            at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:870)
            at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1045)
            at android.app.FragmentManagerImpl.addFragment(FragmentManager.java:1147)
            at android.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2116)
            at android.app.Activity.onCreateView(Activity.java:5328)
            at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:733)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:482)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
            at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
            at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:378)
            at android.app.Activity.setContentView(Activity.java:2145)
            at com.example.adrew.convertmidterm.MainActivity.onCreate(MainActivity.java:14)
            at android.app.Activity.performCreate(Activity.java:5990)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
            at android.app.ActivityThread.access$800(ActivityThread.java:151)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:135)
            at android.app.ActivityThread.main(ActivityThread.java:5257)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
07-09 20:29:02.966  17354-17367/com.example.adrew.convertmidterm W/art﹕ Suspending all threads took: 7.769ms

这是我的代码：

package com.example.adrew.convertmidterm;

import android.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;

import android.view.View.OnClickListener;

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

public MainActivityFragment() {
}

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

    //all test

    //original three without getView().
    //final EditText editCentimeters = (EditText) findViewById(R.id.editCentimeters);

    final EditText editCentimeters = (EditText) getView().findViewById(R.id.editCentimeters);

    final EditText editInches = (EditText) getView().findViewById(R.id.editInches);

    Button buttonConvert = (Button) getView().findViewById(R.id.buttonConvert);

    //buttonConvert.setOnClickListener(new OnClickListener() {
        buttonConvert.setOnClickListener(new View.OnClickListener() {

        @Override
        public void onClick(View arg0) {

            double centimeters = Double.valueOf( editCentimeters.getText().toString());

            double inches = centimeters *  0.393700787 ;

            editInches.setText(String.valueOf(inches));

        }
    });
    //end test
    return rootView;
    }

}

的AndroidManifest.xml：

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

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

</manifest>

Fragment_main.xml如下：

<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:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    android:paddingBottom="@dimen/activity_vertical_margin"
    tools:context=".MainActivityFragment">



    <TextView
        android:id="@+id/textCentimeters"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginTop="34dp"
        android:text="Centimeters:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textInches"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@+id/editCentimeters"
        android:layout_marginTop="40dp"
        android:layout_toLeftOf="@+id/editCentimeters"
        android:text="Inches:"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <EditText
        android:id="@+id/editInches"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textInches"
        android:layout_alignParentRight="true"
        android:ems="10"
        android:inputType="number" />

    <EditText
        android:id="@+id/editCentimeters"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/textCentimeters"
        android:layout_alignParentRight="true"
        android:ems="10"
        android:inputType="number" />

    <Button
        android:id="@+id/buttonConvert"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="Convert" />

</RelativeLayout>

Answer 1

您无法使用getView()作为参考，因为您的View将在return rootView;中创建。

在您致电return rootView;之后

getView()。您收到NullPointerException，因为它尚未创建。

您需要更改

final EditText editCentimeters = (EditText) getView().findViewById(R.id.editCentimeters);

final EditText editInches = (EditText) getView().findViewById(R.id.editInches);

Button buttonConvert = (Button) getView().findViewById(R.id.buttonConvert);

到

final EditText editCentimeters = (EditText) rootView.findViewById(R.id.editCentimeters);

final EditText editInches = (EditText) rootView.findViewById(R.id.editInches);

Button buttonConvert = (Button) rootView.findViewById(R.id.buttonConvert);

为什么模拟器运行后我的应用程序仍然崩溃？

1 个答案: