Android 启动活动时出错，_Android

Android 启动活动时出错，

android

Android 启动活动时出错，,android,Android,我有一个包含按钮的活动，这些按钮将引导我进入下一个活动问题是第一个包含这些按钮的活动给了我这个错误你能解释一下那个错误是什么吗多谢各位 08-06 05:16:53.278: E/AndroidRuntime(771): FATAL EXCEPTION: main 08-06 05:16:53.278: E/AndroidRuntime(771): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.

我有一个包含按钮的活动，这些按钮将引导我进入下一个活动

问题是第一个包含这些按钮的活动给了我这个错误

你能解释一下那个错误是什么吗

多谢各位

08-06 05:16:53.278: E/AndroidRuntime(771): FATAL EXCEPTION: main
08-06 05:16:53.278: E/AndroidRuntime(771): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.lspu.handbook/com.lspu.handbook.apr}: java.lang.NullPointerException
08-06 05:16:53.278: E/AndroidRuntime(771):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2180)
08-06 05:16:53.278: E/AndroidRuntime(771):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2230)
08-06 05:16:53.278: E/AndroidRuntime(771):  at android.app.ActivityThread.access$600(ActivityThread.java:141)
08-06 05:16:53.278: E/AndroidRuntime(771):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1234)
08-06 05:16:53.278: E/AndroidRuntime(771):  at android.os.Handler.dispatchMessage(Handler.java:99)
08-06 05:16:53.278: E/AndroidRuntime(771):  at android.os.Looper.loop(Looper.java:137)
08-06 05:16:53.278: E/AndroidRuntime(771):  at android.app.ActivityThread.main(ActivityThread.java:5039)
08-06 05:16:53.278: E/AndroidRuntime(771):  at java.lang.reflect.Method.invokeNative(Native Method)
08-06 05:16:53.278: E/AndroidRuntime(771):  at java.lang.reflect.Method.invoke(Method.java:511)
08-06 05:16:53.278: E/AndroidRuntime(771):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
08-06 05:16:53.278: E/AndroidRuntime(771):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
08-06 05:16:53.278: E/AndroidRuntime(771):  at dalvik.system.NativeStart.main(Native Method)
08-06 05:16:53.278: E/AndroidRuntime(771): Caused by: java.lang.NullPointerException
08-06 05:16:53.278: E/AndroidRuntime(771):  at com.lspu.handbook.apr.onCreate(apr.java:35)
08-06 05:16:53.278: E/AndroidRuntime(771):  at android.app.Activity.performCreate(Activity.java:5104)
08-06 05:16:53.278: E/AndroidRuntime(771):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1080)
08-06 05:16:53.278: E/AndroidRuntime(771):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2144)
08-06 05:16:53.278: E/AndroidRuntime(771):  ... 11 more

这是我的密码：

public class apr extends Activity implements OnClickListener{

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, 
    WindowManager.LayoutParams.FLAG_FULLSCREEN);

    this.setContentView(R.layout.apr);

    Button ar = (Button)findViewById(R.id.ar);
    ar.setOnClickListener(this);

    Button reg = (Button)findViewById(R.id.reg);
    reg.setOnClickListener(this);

    Button ta = (Button)findViewById(R.id.ta);
    ta.setOnClickListener(this);

    Button vr = (Button)findViewById(R.id.vr);
    vr.setOnClickListener(this);

    Button foreign = (Button)findViewById(R.id.foreign);
    foreign.setOnClickListener(this);

    Button non = (Button)findViewById(R.id.nonreg);
    non.setOnClickListener(this);

    Button cross = (Button)findViewById(R.id.cross);
    cross.setOnClickListener(this);

    Button scholar = (Button)findViewById(R.id.scholar);
    scholar.setOnClickListener(this);

    Button nxt = (Button)findViewById(R.id.lspu_nxt_btn);
    nxt.setOnClickListener(this);




    StartAnimations();
}
     private void StartAnimations() {
            Animation anim = AnimationUtils.loadAnimation(this, R.anim.alpha);
            anim.reset();
            LinearLayout l=(LinearLayout) findViewById(R.id.lspulayout);
            l.clearAnimation();
            l.startAnimation(anim);


            //back button
            Button backButton = (Button)findViewById(R.id.lspu_bak_btn);
            backButton.setOnClickListener(new OnClickListener() {

                public void onClick(View v) {
                    Intent instructionsIntent = new Intent(apr.this,MainBookActivity.class);
                    startActivity(instructionsIntent);
                finish();
                }
             });

            }


     @Override
        public void onDestroy(){
            super.onDestroy();
            System.gc();
            finish();
        }

        @Override
        public void onClick(View v) {
            Intent intent = null;

            switch( v.getId() ) {

            case R.id.ar:
                intent = new Intent(this, Hand_Book_ar.class);
                break;

            case R.id.reg:
                intent = new Intent(this, Hand_Book_reg.class);
                break;

            case R.id.ta:
                intent = new Intent(this, Hand_Book_ta.class);
                break;

            case R.id.vr:
                intent = new Intent(this, Hand_Book_vr.class);
                break;

            case R.id.foreign:
                intent = new Intent(this, Hand_Book_foreign.class);
                break;

            case R.id.nonreg:
                intent = new Intent(this, Hand_Book_nonreg.class);
                break;

            case R.id.cross:
                intent = new Intent(this, Hand_Book_cross.class);
                break;

            case R.id.scholar:
                intent = new Intent(this, Hand_Book_scholar.class);
                break;

            case R.id.lspu_nxt_btn:
                intent = new Intent(this, apr2.class);
                break;


            default:
                Toast toast = Toast.makeText(this, "Do I missed the button you clicked?", Toast.LENGTH_SHORT);
                toast.show();
                break;
            }

            // Open images
            if (intent != null) {
                intent.setAction(intent.ACTION_VIEW);
                startActivity(intent);
            }
        }

         @Override
            public boolean onKeyDown(int keyCode, KeyEvent event) {
                //Handle the back button
                if(keyCode == KeyEvent.KEYCODE_BACK) {
                    //Ask the user if they want to quit
                    new AlertDialog.Builder(this)
                    .setIcon(android.R.drawable.ic_dialog_alert)
                    .setTitle(R.string.quit)
                    .setMessage(R.string.really_quit)
                    .setPositiveButton(R.string.yes, new DialogInterface.OnClickListener() {

                        @Override
                        public void onClick(DialogInterface dialog, int which) {

                            //Stop the activity
                            apr.this.finish();    
                        }

                    })
                    .setNegativeButton(R.string.no, null)
                    .show();

                    return true;
                }
                else {
                    return super.onKeyDown(keyCode, event);
                }

            }
}

以下是xml：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="@drawable/menubg"
    android:orientation="vertical" >
<RelativeLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent" >



        <LinearLayout
            android:id="@+id/lspulayout"
            android:layout_width="fill_parent"
            android:layout_height="fill_parent"
            android:orientation="vertical" >

            <ImageView
                android:id="@+id/tirlw"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="right"
                android:src="@drawable/titleapr" />

            <Button
                android:id="@+id/ar"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
    android:background="@drawable/btnallctr"
    android:gravity="top|center"
    android:text="Admission Requirements"
    android:textSize="17dp" />


            <Button
                android:id="@+id/reg"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_gravity="center"
    android:background="@drawable/btnallctr"
    android:gravity="top|center"
    android:text="Registration"
    android:textSize="17dp" />

            <Button
                android:id="@+id/ta"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
               android:layout_gravity="center"
    android:background="@drawable/btnallctr"
    android:gravity="top|center"
    android:text="Transfer Admision"
    android:textSize="17dp" />

<Button
    android:id="@+id/vr"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:background="@drawable/btnallctr"
    android:gravity="top|center"
    android:text="Validation Requirements"
    android:textSize="17dp" />

<Button
    android:id="@+id/foreign"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:background="@drawable/btnallctr"
    android:gravity="top|center"
    android:text="Foreign Student Admission"
    android:textSize="16sp" />

<Button
    android:id="@+id/nonreg"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:background="@drawable/btnallctr"
    android:gravity="top|center"
    android:text="Non-Regular Admission"
    android:textSize="17sp" />

<Button
    android:id="@+id/cross"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:background="@drawable/btnallctr"
    android:gravity="top|center"
    android:text="Cross Registration"
    android:textSize="18sp" />

<Button
    android:id="@+id/scholar"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="center"
    android:background="@drawable/btnallctr"
    android:gravity="top|center"
    android:text="Scholarship"
    android:textSize="18sp" />
<RelativeLayout
    android:layout_width="fill_parent"
    android:layout_height="wrap_content" >
<Button
    android:id="@+id/lspu_bak_btn"
    android:layout_width="40dp"
    android:layout_height="30dp"
    android:layout_gravity="bottom|left"
    android:layout_marginTop="10dp"
    android:background="@drawable/backbtncntrl_hd" />

<Button
    android:id="@+id/lspu_nxt_btn"
    android:layout_width="40dp"
    android:layout_height="30dp"
    android:layout_alignParentBottom="true"
    android:layout_alignParentRight="true"
    android:layout_alignTop="@+id/lspu_bak_btn"
    android:background="@drawable/nxtbtncntrl_hd" />

</RelativeLayout>

        </LinearLayout>



    </RelativeLayout>
</LinearLayout>

感谢那些帮忙的人

在com.lspu.handbook.apr.onCreate（apr.java:35）

指出按钮未初始化，或者换句话说，它是空的。在您的代码中，您正在实例化

onCreate（）

方法中的

按钮

对象，因此所有这些按钮都具有

onCreate（）的本地作用域

一旦onCreate（）返回，这些按钮就超出了作用域，因此当您单击任何按钮时，就会得到

NullPointerException

。简单的解决方案是在方法外部创建所有按钮对象，然后在

onCreate（）

内部实例化它们

}

这是一个例外。检查第35行的代码。08-06 05:16:53.278:E/AndroidRuntime（771）：原因：java.lang.NullPointerException 08-06 05:16:53.278:E/AndroidRuntime（771）：在com.lspu.handbook.apr.onCreate（apr.java:35）发布代码。请在第35行发布异常，检查您的35行codepost u r xml文件，这将有助于跟踪错误。可能此处使用的id不在xml中file@Jerome发生这种情况的只是post u r xml，人们希望在这里展示他们非常聪明。post u r xml让我们看看问题出在哪里

 Button ar,reg,ta,vr,foreign,non,cross,scholar,nxt;

 @Override
 public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN, 
WindowManager.LayoutParams.FLAG_FULLSCREEN);

this.setContentView(R.layout.apr);

 ar = (Button)findViewById(R.id.ar);
ar.setOnClickListener(this);

 reg = (Button)findViewById(R.id.reg);
reg.setOnClickListener(this);

 ta = (Button)findViewById(R.id.ta);
ta.setOnClickListener(this);

 vr = (Button)findViewById(R.id.vr);
vr.setOnClickListener(this);

 foreign = (Button)findViewById(R.id.foreign);
foreign.setOnClickListener(this);

 non = (Button)findViewById(R.id.nonreg);
non.setOnClickListener(this);

 cross = (Button)findViewById(R.id.cross);
cross.setOnClickListener(this);

 scholar = (Button)findViewById(R.id.scholar);
scholar.setOnClickListener(this);

 nxt = (Button)findViewById(R.id.lspu_nxt_btn);
nxt.setOnClickListener(this);




StartAnimations();