无法在 Android 应用程序的同一视图上添加按钮和文本视图 - 非法状态异常

Question

我对 Android 应用程序有点陌生，我正在尝试与它们一起玩，以更好地了解它们的工作方式。现在我正在为 android 构建您的第一个应用程序，您可以在其中将消息传递给另一个活动。我想显示该消息并有另一个可能转到另一个活动的按钮，但我无法弄清楚我的错误。我得到一个 IllegalStateException - 孩子已经有一个父母，当我尝试将 textview 和按钮添加到我的相对布局时，您必须首先在孩子的父母上调用 removeView()。我已经尝试删除这两个功能，但我的布局不包括按钮。我不确定我为什么会收到这个错误，或者我是否正在接近这个布局错误。任何帮助/建议将不胜感激，谢谢！

这是我的应用程序的代码

package com.example.app;

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

public class DisplayMessageActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Intent intent = getIntent();

        // Set the text view as the activity layout
        setContentView(R.layout.fragment_display_message);
        String message = intent.getStringExtra(MainActivity.EXTRA_MESSAGE);
        TextView textView = (TextView) this.findViewById(R.id.text_view);
        textView.setTextSize(20);
        message = "The current address is " + message;
        textView.setText(message);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {

        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.display_message, 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_display_message,
                    container, false);
            return rootView;
        }
    }

}

这是清单

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.app"
    android:versionCode="1"
    android:versionName="1.0" >
    <uses-permission android:name="android.permission.CAMERA"/>
    <uses-feature android:name="android.hardware.camera" />
    <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.example.app.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.dm.zbar.android.scanner.ZBarScannerActivity"
        android:screenOrientation="landscape"
        android:label="@string/app_name" />
        <activity
        android:name="com.example.app.DisplayMessageActivity"
        android:label="@string/title_activity_display_address"
        android:parentActivityName="com.example.app.MainActivity" >
        <meta-data
            android:name="android.support.PARENT_ACTIVITY"
            android:value="com.example.myfirstapp.MainActivity" />
    </activity>
        <activity android:name="AddressChange"></activity>

    </application>

</manifest>

Fragment_main.xml

    <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/relative_layout"
    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=".DisplayMessageActivity" >

    <TextView
        android:id="@+id/text_view"
        android:layout_width="150dp"
        android:layout_height="114dp" />

    <Button
        android:id="@+id/back"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="Back"
        android:text="@string/back" />

</LinearLayout>

logcat 文件

06-04 15:22:55.380: E/AndroidRuntime(820): FATAL EXCEPTION: main
06-04 15:22:55.380: E/AndroidRuntime(820): Process: com.example.app, PID: 820
06-04 15:22:55.380: E/AndroidRuntime(820): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.app/com.example.app.DisplayMessageActivity}: java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2208)
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2270)
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.app.ActivityThread.access$800(ActivityThread.java:138)
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1209)
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.os.Handler.dispatchMessage(Handler.java:102)
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.os.Looper.loop(Looper.java:136)
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.app.ActivityThread.main(ActivityThread.java:5042)
06-04 15:22:55.380: E/AndroidRuntime(820):  at java.lang.reflect.Method.invokeNative(Native Method)
06-04 15:22:55.380: E/AndroidRuntime(820):  at java.lang.reflect.Method.invoke(Method.java:515)
06-04 15:22:55.380: E/AndroidRuntime(820):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:776)
06-04 15:22:55.380: E/AndroidRuntime(820):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:601)
06-04 15:22:55.380: E/AndroidRuntime(820):  at dalvik.system.NativeStart.main(Native Method)
06-04 15:22:55.380: E/AndroidRuntime(820): Caused by: java.lang.IllegalStateException: The specified child already has a parent. You must call removeView() on the child's parent first.
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.view.ViewGroup.addViewInner(ViewGroup.java:3562)
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.view.ViewGroup.addView(ViewGroup.java:3415)
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.view.ViewGroup.addView(ViewGroup.java:3360)
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.view.ViewGroup.addView(ViewGroup.java:3336)
06-04 15:22:55.380: E/AndroidRuntime(820):  at com.example.app.DisplayMessageActivity.onCreate(DisplayMessageActivity.java:35)
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.app.Activity.performCreate(Activity.java:5231)
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087)
06-04 15:22:55.380: E/AndroidRuntime(820):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2172)
06-04 15:22:55.380: E/AndroidRuntime(820):  ... 11 more

Answer 1

xml 布局会为您完成所有视图的添加。通过自己做，您可以为一个视图创建 2 个父级，这是非法的。幸运的是，在这种情况下，您只是在做不需要的工作，因此您可以删除这些行。