java - 从另一个类获取 String[]

Question

这是我的主课:

public class MainActivity extends AppCompatActivity {

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

Context con;

protected void onClickCityBreak(View v) {

    String [] arrayCityBreak = con.getResources().getStringArray(R.array.citybreak);
    Intent myintent = new Intent(MainActivity.this, ActivityTo.class);
    myintent.putExtra("PLACES",arrayCityBreak);
    startActivity(myintent);
}
}

这是我想要将我的 Intent 数组发送到的类:

public class ActivityTo extends ListActivity {
@Override
protected void onCreate(Bundle savedInstanceState){
    super.onCreate(savedInstanceState);

    String[] arrayCityBreak = getIntent().getStringArrayExtra("PLACES");

    ArrayAdapter<String> adapterCityBreak = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayCityBreak);

    ListView myview = getListView();

    myview.setAdapter(adapterCityBreak);

}
}

我的 AndroidManifest.xml 文件:

<activity android:name=".MainActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN" />

            <category android:name="android.intent.category.LAUNCHER" />
        </intent-filter>
    </activity>

    <activity android:name=".ActivityTo">

    </activity>

我找不到这方面的问题。当我单击按钮以获取新 Intent 时，我的应用程序将关闭。这是因为我尝试发送 String[]，但我不明白为什么它不起作用。

--------- beginning of crash
E/AndroidRuntime: FATAL EXCEPTION: main
              Process: com.ivarrreyna.assignment, PID: 2626
              java.lang.IllegalStateException: Could not execute method for android:onClick
                  at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:293)
                  at android.view.View.performClick(View.java:5198)
                  at android.view.View$PerformClick.run(View.java:21147)
                  at android.os.Handler.handleCallback(Handler.java:739)
                  at android.os.Handler.dispatchMessage(Handler.java:95)
                  at android.os.Looper.loop(Looper.java:148)
                  at android.app.ActivityThread.main(ActivityThread.java:5417)
                  at java.lang.reflect.Method.invoke(Native Method)
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
               Caused by: java.lang.reflect.InvocationTargetException
                  at java.lang.reflect.Method.invoke(Native Method)
                  at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288)
                  at android.view.View.performClick(View.java:5198) 
                  at android.view.View$PerformClick.run(View.java:21147) 
                  at android.os.Handler.handleCallback(Handler.java:739) 
                  at android.os.Handler.dispatchMessage(Handler.java:95) 
                  at android.os.Looper.loop(Looper.java:148) 
                  at android.app.ActivityThread.main(ActivityThread.java:5417) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
               Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference
                  at com.ivarrreyna.assignment.MainActivity.onClickCityBreak(MainActivity.java:24)
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at android.support.v7.app.AppCompatViewInflater$DeclaredOnClickListener.onClick(AppCompatViewInflater.java:288) 
                  at android.view.View.performClick(View.java:5198) 
                  at android.view.View$PerformClick.run(View.java:21147) 
                  at android.os.Handler.handleCallback(Handler.java:739) 
                  at android.os.Handler.dispatchMessage(Handler.java:95) 
                  at android.os.Looper.loop(Looper.java:148) 
                  at android.app.ActivityThread.main(ActivityThread.java:5417) 
                  at java.lang.reflect.Method.invoke(Native Method) 
                  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
                  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 

应用程序已终止。

Answer 1

无需将数组传递给 ，因为 ActivityTo 也是一个 Activity ，因此也可以在此处获取资源数组

public class ActivityTo extends ListActivity {

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

        String [] arrayCityBreak = getResources().getStringArray(R.array.citybreak);

        ArrayAdapter<String> adapterCityBreak = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, arrayCityBreak);

        ListView myview = getListView();

        myview.setAdapter(adapterCityBreak);

    }
}

<小时/>

要删除当前错误，

要么这样做

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

或

在MainActivity中使用它，因为con未初始化

  String [] arrayCityBreak = getResources().getStringArray(R.array.citybreak);

而不是

  String [] arrayCityBreak = con.getResources().getStringArray(R.array.citybreak);