嘗試將值從一個活動傳遞到另一個活動時，出現NullPointer異常

Question

我正在嘗試實現一個onItemClicklister() ，其中單擊一個項目時，文本值將從一個活動轉移到另一個活動。 下面是代碼片段。

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

                String name = ((TextView) view.findViewById(R.id.title)).getText().toString();
                String cost = ((TextView) view.findViewById(R.id.artist)).getText().toString();
                String description = ((TextView) view.findViewById(R.id.duration)).getText().toString();

                // Starting new intent
                Intent in = new Intent(getApplicationContext(), SingleMenuItemActivity.class);
                in.putExtra(KEY_TITLE, name);
                in.putExtra(KEY_ARTIST, cost);
                in.putExtra(KEY_DURATION, description);
                startActivity(in);

            }
        });

下一個活動

public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
//        setContentView(R.layout.single_list_item);

        // getting intent data
        Intent in = getIntent();

        // Get JSON values from previous intent
        String name = in.getStringExtra(KEY_TITLE);
        String cost = in.getStringExtra(KEY_ARTIST);
        String description = in.getStringExtra(KEY_DURATION);

//         Displaying all values on the screen
        TextView lblName = (TextView) findViewById(R.id.name_label);
        TextView lblCost = (TextView) findViewById(R.id.email_label);
        TextView lblDesc = (TextView) findViewById(R.id.mobile_label);

        lblName.setText(name);
        lblCost.setText(cost);
        lblDesc.setText(description);
    }

但是它拋出一個

E/AndroidRuntime(  626): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.eve_haps/com.example.eve_haps.SingleMenuItemActivity}: java.lang.NullPointerException
E/AndroidRuntime(  626):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1956)
E/AndroidRuntime(  626):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1981)
E/AndroidRuntime(  626):    at android.app.ActivityThread.access$600(ActivityThread.java:123)
E/AndroidRuntime(  626):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1147)
E/AndroidRuntime(  626):    at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(  626):    at android.os.Looper.loop(Looper.java:137)
E/AndroidRuntime(  626):    at android.app.ActivityThread.main(ActivityThread.java:4424)
E/AndroidRuntime(  626):    at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(  626):    at java.lang.reflect.Method.invoke(Method.java:511)
E/AndroidRuntime(  626):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
E/AndroidRuntime(  626):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
E/AndroidRuntime(  626):    at dalvik.system.NativeStart.main(Native Method)
E/AndroidRuntime(  626): Caused by: java.lang.NullPointerException
E/AndroidRuntime(  626):    at com.example.eve_haps.SingleMenuItemActivity.onCreate(SingleMenuItemActivity.java:32)
E/AndroidRuntime(  626):    at android.app.Activity.performCreate(Activity.java:4465)
E/AndroidRuntime(  626):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049)
E/AndroidRuntime(  626):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1920)

我似乎不知道問題出在什么地方。謝謝您的幫助。

Answer 1

取消對SingleMenuItemActivity的 onCreate()代碼行的注釋。

setContentView(R.layout.single_list_item);

我認為您的TextViews為null。

NullPointerException來自這些行，

lblName.setText(name);
lblCost.setText(cost);
lblDesc.setText(description);