Question

在模拟器中启动应用程序时停止应用程序。我找不到任何问题。

这是logcat：

FATAL EXCEPTION: main
java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{com.twy.rsmap/com.twy.rsmap.MainActivity}: java.lang.NullPointerException
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1879)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
        at android.app.ActivityThread.access$600(ActivityThread.java:122)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
        at android.os.Handler.dispatchMessage(Handler.java:99)
        at android.os.Looper.loop(Looper.java:137)
        at android.app.ActivityThread.main(ActivityThread.java:4340)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:511)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.NullPointerException
        at android.app.Activity.findViewById(Activity.java:1794)
        at com.twy.rsmap.MainActivity.<init>(MainActivity.java:173)
        at java.lang.Class.newInstanceImpl(Native Method)
        at java.lang.Class.newInstance(Class.java:1319)
        at android.app.Instrumentation.newActivity(Instrumentation.java:1023)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1870)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980)
            at android.app.ActivityThread.access$600(ActivityThread.java:122)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146)
            at android.os.Handler.dispatchMessage(Handler.java:99)
            at android.os.Looper.loop(Looper.java:137)
            at android.app.ActivityThread.main(ActivityThread.java:4340)
            at java.lang.reflect.Method.invokeNative(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:511)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551)
            at dalvik.system.NativeStart.main(Native Method)

如何找出问题？（MainActivity.java:173和MainActivity.java:174）

Button[] buttons = new Button[]{(Button)findViewById(R.id.FileToolStripMenuItem),(Button)findViewById(R.id.ImageToolStripMenuItem),(Button)findViewById(R.id.GroundToolStripMenuItem),(Button)findViewById(R.id.SeaToolStripMenuItem),(Button)findViewById(R.id.NailToolStripMenuItem),(Button)findViewById(R.id.RubberToolStripMenuItem),(Button)findViewById(R.id.SpeedboardToolStripMenuItem),(Button)findViewById(R.id.ItemToolStripMenuItem)};
LinearLayout[] lls = new LinearLayout[]{(LinearLayout)findViewById(R.id.FileDrop),(LinearLayout)findViewById(R.id.ImageDrop),(LinearLayout)findViewById(R.id.GroundDrop),(LinearLayout)findViewById(R.id.SeaDrop),(LinearLayout)findViewById(R.id.NailDrop),(LinearLayout)findViewById(R.id.RubberDrop),(LinearLayout)findViewById(R.id.SpeedDrop),(LinearLayout)findViewById(R.id.ItemDrop)};

这之前运作正常，但在做某事后发生了一些事情。也许与版本有关？

对象数组不太好，所以在我替换

之后

Button[] buttons = new Button[]{(Button)findViewById(R.id.FileToolStripMenuItem),(Button)findViewById(R.id.ImageToolStripMenuItem),(Button)findViewById(R.id.GroundToolStripMenuItem),(Button)findViewById(R.id.SeaToolStripMenuItem),(Button)findViewById(R.id.NailToolStripMenuItem),(Button)findViewById(R.id.RubberToolStripMenuItem),(Button)findViewById(R.id.SpeedboardToolStripMenuItem),(Button)findViewById(R.id.ItemToolStripMenuItem)};
LinearLayout[] lls = new LinearLayout[]{(LinearLayout)findViewById(R.id.FileDrop),(LinearLayout)findViewById(R.id.ImageDrop),(LinearLayout)findViewById(R.id.GroundDrop),(LinearLayout)findViewById(R.id.SeaDrop),(LinearLayout)findViewById(R.id.NailDrop),(LinearLayout)findViewById(R.id.RubberDrop),(LinearLayout)findViewById(R.id.SpeedDrop),(LinearLayout)findViewById(R.id.ItemDrop)};

通过

int[] idb = {R.id.FileToolStripMenuItem,R.id.ImageToolStripMenuItem,R.id.GroundToolStripMenuItem,R.id.SeaToolStripMenuItem,R.id.NailToolStripMenuItem,R.id.RubberToolStripMenuItem,R.id.SpeedboardToolStripMenuItem,R.id.ItemToolStripMenuItem};
int[] idl = {R.id.FileDrop,R.id.ImageDrop,R.id.GroundDrop,R.id.SeaDrop,R.id.NailDrop,R.id.RubberDrop,R.id.SpeedDrop,R.id.ItemDrop};

并将代码替换为(Button)findViewById(int[index])

（来自

        int a ;
        for (a=0;a<buttons.length;a++){
            buttons[a].setVisibility(View.VISIBLE);
        }

到

        int a ;
        for (a=0;a<idb.length;a++){
            Button button1 = (Button)findViewById(idb[a]);
            button1.setVisibility(View.VISIBLE);
        }

）

问题解决了。

Answer 1

它的说法显然你在这里有问题。

            Caused by: java.lang.NullPointerException
            at android.app.Activity.findViewById(Activity.java:1794)
            at com.twy.rsmap.MainActivity.<init>(MainActivity.java:173)

Answer 2

所以，这是一个错误堆栈跟踪。它会显示应用程序崩溃时调用的内容。在查看其中一个时，通常最有用的是找到对您自己的应用程序的引用（而不是大多数行的Android操作系统）并从那里开始。在你的例子中，我看到：

    at com.twy.rsmap.MainActivity.<init>(MainActivity.java:173)

因此，请查看MainActivity的第173行，了解空指针异常。

Answer 3

无法实例化活动ComponentInfo 答由于 NullPointer异常＆amp;由于findViewById（）检查 findviewById 中使用的XML ID和Java代码ID，因此出现空指针异常。检查 MainActivity Line No 173

Answer 4

对象数组不太好，所以在我替换

之后

Button[] buttons = new Button[]{(Button)findViewById(R.id.FileToolStripMenuItem),(Button)findViewById(R.id.ImageToolStripMenuItem),(Button)findViewById(R.id.GroundToolStripMenuItem),(Button)findViewById(R.id.SeaToolStripMenuItem),(Button)findViewById(R.id.NailToolStripMenuItem),(Button)findViewById(R.id.RubberToolStripMenuItem),(Button)findViewById(R.id.SpeedboardToolStripMenuItem),(Button)findViewById(R.id.ItemToolStripMenuItem)};
LinearLayout[] lls = new LinearLayout[]{(LinearLayout)findViewById(R.id.FileDrop),(LinearLayout)findViewById(R.id.ImageDrop),(LinearLayout)findViewById(R.id.GroundDrop),(LinearLayout)findViewById(R.id.SeaDrop),(LinearLayout)findViewById(R.id.NailDrop),(LinearLayout)findViewById(R.id.RubberDrop),(LinearLayout)findViewById(R.id.SpeedDrop),(LinearLayout)findViewById(R.id.ItemDrop)};

通过

int[] idb = {R.id.FileToolStripMenuItem,R.id.ImageToolStripMenuItem,R.id.GroundToolStripMenuItem,R.id.SeaToolStripMenuItem,R.id.NailToolStripMenuItem,R.id.RubberToolStripMenuItem,R.id.SpeedboardToolStripMenuItem,R.id.ItemToolStripMenuItem};
int[] idl = {R.id.FileDrop,R.id.ImageDrop,R.id.GroundDrop,R.id.SeaDrop,R.id.NailDrop,R.id.RubberDrop,R.id.SpeedDrop,R.id.ItemDrop};

并将代码替换为(Button)findViewById(int[index])

（来自

        int a ;
        for (a=0;a<buttons.length;a++){
            buttons[a].setVisibility(View.VISIBLE);
        }

到

        int a ;
        for (a=0;a<idb.length;a++){
            Button button1 = (Button)findViewById(idb[a]);
            button1.setVisibility(View.VISIBLE);
        }

）

问题解决了。

不幸的是XXX已停止了。如何解决这个问题？

4 个答案: