Question

我遇到的问题是我无法开始活动。

以下是开始新活动之前上一个活动的代码：

public class MainActivity extends ActionBarActivity {

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

        populateListView();
        registerClickCallback();
    }

    private void registerClickCallback() {
        ListView list = (ListView)findViewById(R.id.listViewTop100);

        list.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                    int position, long id) {

                Intent intent;
                switch(position)
                {
                case 0:
                    intent = new Intent(MainActivity.this,NextactivityActivity.class);
                    startActivity(intent);
                    break;
                case 1:
                    intent = new Intent(MainActivity.this,NextTvSeriesActivity.class);
                    startActivity(intent);
                    break;
                case 2:
                    intent = new Intent(MainActivity.this,Next100moviesActivity.class);
                    startActivity(intent);
                    break;
                default:
                    break;
                }

            }
        });

    }

（我想要开始的活动是案例1 / NextTvSeriesActivity）这是我想要开始的活动的代码：

package com.example.its_time.mainmenu;

import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;

import com.example.its_time.R;

public class NextTvSeriesActivity extends ActionBarActivity {

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

        pupulateListView();
        registerClickCallback();

    }

    private void registerClickCallback() {

ListView list = (ListView)findViewById(R.id.listViewTop100);

        list.setOnItemClickListener(new AdapterView.OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> parent, View view,
                    int position, long id) {

                Intent intent;
                switch(position)
                {
                case 0:
                    intent = new Intent(NextTvSeriesActivity.this,TvSeriesActiongenreActivity.class);
                    startActivity(intent);
                    break;
                case 1:
                    intent = new Intent(NextTvSeriesActivity.this,TvSeriesAnimationgenreActivity.class);
                    startActivity(intent);
                    break;
                default:
                    break;
                }

            }
        });
    }

这是android清单代码：

<activity
            android:name="com.example.its_time.mainmenu.NextTvSeriesActivity"
            android:label="@string/title_activity_next_tv_series" >
        </activity>

com.example.its_time.mainmenu是包namne。

我检查过清单文件，拼写是否正确，活动是在同一个文件夹中，可能是什么错误？

以下是整个错误：

12-20 19:43:53.037: E/AndroidRuntime(2071): FATAL EXCEPTION: main
12-20 19:43:53.037: E/AndroidRuntime(2071): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.its_time/com.example.its_time.mainmenu.NextTvSeriesActivity}: java.lang.NullPointerException
12-20 19:43:53.037: E/AndroidRuntime(2071):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at android.app.ActivityThread.access$600(ActivityThread.java:123)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at android.os.Handler.dispatchMessage(Handler.java:99)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at android.os.Looper.loop(Looper.java:137)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at android.app.ActivityThread.main(ActivityThread.java:4424)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at java.lang.reflect.Method.invokeNative(Native Method)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at java.lang.reflect.Method.invoke(Method.java:511)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at dalvik.system.NativeStart.main(Native Method)
12-20 19:59:15.371: E/AndroidRuntime(3182): Caused by: java.lang.NullPointerException
12-20 19:59:15.371: E/AndroidRuntime(3182):     at com.example.its_time.mainmenu.NextTvSeriesActivity.registerClickCallback(NextTvSeriesActivity.java:29)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at com.example.its_time.mainmenu.NextTvSeriesActivity.onCreate(NextTvSeriesActivity.java:21)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at android.app.Activity.performCreate(Activity.java:4465)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
12-20 19:59:15.371: E/AndroidRuntime(3182):     at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)
12-20 19:59:15.371: E/AndroidRuntime(3182):     ... 11 more

Answer 1

在next_tv_series中调用时，您的listViewTop100布局没有ID findViewById()的视图，NextTvSeriesActivity.registerClickCallback()返回null。在null上调用方法（setOnItemClickListener()）会导致异常。

无法启动活动组件信息？

1 个答案: