Question

我在我的主要活动中将arrayList传递给另一个活动：

Intent i = new Intent(getApplicationContext(),PairedDevices.class);
i.putExtra("arrayListPaired", arrayListpaired);
startActivity(i);

要传递给名为PairedDevices的actvity，我要显示该数组列表。这是PairedDevices类：

public class PairedDevices extends Activity {
    ListView listViewPaired;
    ArrayList<String> pairedDevices = (ArrayList<String>) getIntent().getSerializableExtra("arrayListPaired");
    ArrayAdapter<String> listAdapter;

    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_paired_devices);
        listViewPaired = (ListView)findViewById(R.id.listViewPaired);

        listAdapter = new ArrayAdapter<String>(PairedDevices.this, android.R.layout.simple_list_item_1, pairedDevices);
        listViewPaired.setAdapter(listAdapter);
    }
}

它崩溃了，我得到了以下的堆栈跟踪，如何解决这个问题的任何建议将非常感谢！：

10-28 02:04:10.101  25536-25536/my.obd2connector E/AndroidRuntime﹕ FATAL EXCEPTION: main
    Process: my.obd2connector, PID: 25536
    java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{my.obd2connector/my.obd2connector.PairedDevices}: java.lang.NullPointerException
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2231)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2363)
            at android.app.ActivityThread.access$900(ActivityThread.java:161)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1265)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:157)
            at android.app.ActivityThread.main(ActivityThread.java:5356)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
            at dalvik.system.NativeStart.main(Native Method)
     Caused by: java.lang.NullPointerException
            at my.obd2connector.PairedDevices.<init>(PairedDevices.java:17)
            at java.lang.Class.newInstanceImpl(Native Method)
            at java.lang.Class.newInstance(Class.java:1208)
            at android.app.Instrumentation.newActivity(Instrumentation.java:1079)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2222)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2363)
            at android.app.ActivityThread.access$900(ActivityThread.java:161)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1265)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:157)
            at android.app.ActivityThread.main(ActivityThread.java:5356)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:515)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1265)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1081)
            at dalvik.system.NativeStart.main(Native Method)

Answer 1

将此代码放在onCreate（）;

中

ArrayList<String> pairedDevices = (ArrayList<String>) getIntent().getSerializableExtra("arrayListPaired");

Answer 2

将其放入onCreate

pairedDevices = (ArrayList<String>) getIntent().getSerializableExtra("arrayListPaired");

像这样

public class PairedDevices extends Activity 
{
    ListView listViewPaired;
    ArrayList<String> pairedDevices = null; 
    ArrayAdapter<String> listAdapter;

    public void onCreate(Bundle savedInstanceState) 
    {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.activity_paired_devices);
         listViewPaired = (ListView)findViewById(R.id.listViewPaired);
         pairedDevices = (ArrayList<String>)getIntent().getSerializableExtra("arrayListPaired");
         listAdapter = new ArrayAdapter<String>(PairedDevices.this, android.R.layout.simple_list_item_1, pairedDevices);
         listViewPaired.setAdapter(listAdapter);
    }
}

Answer 3

替换此代码以解决您的错误

Intent i = new Intent（getApplicationContext（），PairedDevices.class）;

i.putStringArrayListExtra（＆＃34; arrayListPaired＆＃34;，arrayListpaired）;

startActivity（ⅰ）;

此代码替换为PairedDevices文件

的ArrayList＆LT; String＆GT; pairedDevices =（ArrayList＆lt; String＆gt;）getIntent（）。getStringArrayListExtra（＆＃34; arrayListPaired＆＃34;）;

使用Intent中传递的arrayList时出错

3 个答案: