Question

我有一个奇怪的问题，我在layout-large-land中创建了一个xml，并且我已经放置了一些按钮我已经为该xml文件编写了一个活动，然后检查它是否在大屏幕中是横向的我写了点击按钮但不幸的是它说空指针异常我不明白我做错了什么，我正在检查我的三星Tab3

这是我的xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <FrameLayout
        android:id="@+id/tabContent"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </FrameLayout>

    <ScrollView
        android:layout_width="90dp"
        android:layout_height="match_parent" >

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:orientation="vertical" >

            <Button
                android:id="@+id/topPick"
                android:layout_width="match_parent"
                android:layout_height="70dip"
                android:layout_marginTop="100dip" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="70dip" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="70dip" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="70dip" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="70dip" />
        </LinearLayout>
    </ScrollView>

</RelativeLayout>

这是我的活动

  import android.content.Context;
import android.content.pm.ActivityInfo;
import android.content.res.Configuration;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends FragmentActivity {
    Button topPick;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        if (isTablet(MainActivity.this)) {
            // tablet
            setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
            setContentView(R.layout.main);
            topPick = (Button) findViewById(R.id.topPick);

            topPick.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    // TODO Auto-generated method stub
                    Toast.makeText(getApplicationContext(), "yyyyyyy", 2000)
                            .show();
                }
            });

        } else {
            // phone
            setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

            setContentView(R.layout.main);
        }
    }

    public boolean isTablet(Context context) {
        boolean xlarge = ((context.getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) == 4);
        boolean large = ((context.getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) == Configuration.SCREENLAYOUT_SIZE_LARGE);
        return (xlarge || large);
    }

}

这是我的清单

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

这是我的logcat

06-21 15:41:44.900: E/AndroidRuntime(30469): FATAL EXCEPTION: main
06-21 15:41:44.900: E/AndroidRuntime(30469): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.screentest/com.example.screentest.MainActivity}: java.lang.NullPointerException
06-21 15:41:44.900: E/AndroidRuntime(30469):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2249)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2299)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at android.app.ActivityThread.access$700(ActivityThread.java:154)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1284)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at android.os.Handler.dispatchMessage(Handler.java:99)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at android.os.Looper.loop(Looper.java:137)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at android.app.ActivityThread.main(ActivityThread.java:5306)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at java.lang.reflect.Method.invokeNative(Native Method)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at java.lang.reflect.Method.invoke(Method.java:511)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1102)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:869)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at dalvik.system.NativeStart.main(Native Method)
06-21 15:41:44.900: E/AndroidRuntime(30469): Caused by: java.lang.NullPointerException
06-21 15:41:44.900: E/AndroidRuntime(30469):  at com.example.screentest.MainActivity.onCreate(MainActivity.java:27)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at android.app.Activity.performCreate(Activity.java:5255)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1097)
06-21 15:41:44.900: E/AndroidRuntime(30469):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2213)

Answer 1

您的代码工作正常。请参阅我在eclipse中编写的代码，并查看附带的屏幕截图。

XML文件

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <FrameLayout
        android:id="@+id/tabContent"
        android:layout_width="match_parent"
        android:layout_height="match_parent" >
    </FrameLayout>

    <ScrollView
        android:layout_width="90dp"
        android:layout_height="match_parent" >

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:orientation="vertical" >

            <Button
                android:id="@+id/topPick"
                android:layout_width="match_parent"
                android:layout_height="70dip"
                android:layout_marginTop="100dip" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="70dip" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="70dip" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="70dip" />

            <Button
                android:layout_width="match_parent"
                android:layout_height="70dip" />
        </LinearLayout>
    </ScrollView>

</RelativeLayout>

JAVA文件

import android.content.Context;
import android.content.pm.ActivityInfo;
import android.content.res.Configuration;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends FragmentActivity {
    Button topPick;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        if (isTablet(MainActivity.this)) {
            // tablet
            setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
            setContentView(R.layout.activity_main);
            topPick = (Button) findViewById(R.id.topPick);
            topPick.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    Toast.makeText(getApplicationContext(), "yyyyyyy", 2000)
                            .show();
                }
            });
        } else {
            // phone
            setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);
            setContentView(R.layout.activity_main);
        }
    }

    public boolean isTablet(Context context) {
        boolean xlarge = ((context.getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) == 4);
        boolean large = ((context.getResources().getConfiguration().screenLayout & Configuration.SCREENLAYOUT_SIZE_MASK) == Configuration.SCREENLAYOUT_SIZE_LARGE);
        return (xlarge || large);
    }
}

Screenshot

在布局 - 大土地按钮中的空指针

1 个答案: