Question

我最近自己学习了android。我按照我的教科书尝试使用片段但即使我输入与我的教科书完全相同的代码，我也遇到了错误。

你们能告诉我什么是错的吗？

这是MainActivity.java

package com.example.ex_1;

import android.app.Activity;
import android.os.Bundle;
import android.support.v4.app.Fragment;
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.TextView;

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }
    public static class CounterFragment extends Fragment {

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
                Bundle savedInstanceState) {
            // TODO Auto-generated method stub

            View root = inflater.inflate(R.layout.counterfragment, container, false);
            Button btnIncrease = (Button)root.findViewById(R.id.btnincrease);
            final TextView textCounter = (TextView)root.findViewById(R.id.txtcounter);
            btnIncrease.setOnClickListener(new Button.OnClickListener() {
                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub
                    int count = Integer.parseInt(textCounter.getText().toString());
                    textCounter.setText(Integer.toString(count + 1));
                }

            });
            return root;
        }

    }
}

这是activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/LinearLayout1"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="${relativePackage}.${activityClass}" >

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="~~"/>
    <fragment 
        android:name="com.example.ex_1.MainActivity$CounterFragment"
        android:id="@+id/counterfragment"
        android:layout_width="match_parent"
        android:layout_height="wrap_content" />

</LinearLayout>

错误是

09-24 07:40:08.329: E/AndroidRuntime(1794): FATAL EXCEPTION: main
09-24 07:40:08.329: E/AndroidRuntime(1794): Process: com.example.ex_1, PID: 1794
09-24 07:40:08.329: E/AndroidRuntime(1794): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.ex_1/com.example.ex_1.MainActivity}: android.view.InflateException: Binary XML file line #13: Error inflating class fragment
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2298)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2360)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.ActivityThread.access$800(ActivityThread.java:144)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1278)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.os.Handler.dispatchMessage(Handler.java:102)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.os.Looper.loop(Looper.java:135)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.ActivityThread.main(ActivityThread.java:5221)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at java.lang.reflect.Method.invoke(Native Method)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at java.lang.reflect.Method.invoke(Method.java:372)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)
09-24 07:40:08.329: E/AndroidRuntime(1794): Caused by: android.view.InflateException: Binary XML file line #13: Error inflating class fragment
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:763)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.view.LayoutInflater.rInflate(LayoutInflater.java:806)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.view.LayoutInflater.inflate(LayoutInflater.java:504)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.view.LayoutInflater.inflate(LayoutInflater.java:414)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.view.LayoutInflater.inflate(LayoutInflater.java:365)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:377)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.Activity.setContentView(Activity.java:2144)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at com.example.ex_1.MainActivity.onCreate(MainActivity.java:19)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.Activity.performCreate(Activity.java:5937)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2251)
09-24 07:40:08.329: E/AndroidRuntime(1794):     ... 10 more
09-24 07:40:08.329: E/AndroidRuntime(1794): Caused by: android.app.Fragment$InstantiationException: Trying to instantiate a class com.example.ex_1.MainActivity$CounterFragment that is not a Fragment
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.Fragment.instantiate(Fragment.java:606)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.Fragment.instantiate(Fragment.java:582)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.FragmentManagerImpl.onCreateView(FragmentManager.java:2108)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.app.Activity.onCreateView(Activity.java:5286)
09-24 07:40:08.329: E/AndroidRuntime(1794):     at android.view.LayoutInflater.createViewFromTag(LayoutInflater.java:733)
09-24 07:40:08.329: E/AndroidRuntime(1794):     ... 20 more
09-24 07:40:08.329: E/AndroidRuntime(1794): Caused by: java.lang.ClassCastException
09-24 07:40:08.329: E/AndroidRuntime(1794):     ... 25 more

Answer 1

问题是你将api级别设置得太低，所以它使用＆＃34; support＆＃34;片段的版本，而不是＆＃34; base＆＃34;片段

put＆＃34; min api level＆＃34;在你的androidmanifest中的11，删除依赖于＆＃34;支持＆＃34;库，删除＆＃34;导入android.support.v4.app.Fragment＆＃34;并用＆＃34; import android.app.fragment＆＃34;替换它。它应该工作

Answer 2

更改

public class MainActivity extends Activity {

到

public class MainActivity extends FragmentActivity {

在Android中使用Fragment时出现ClassCastException

2 个答案: