android studio 应用程序崩溃

Question

Could anyone please help me as my android studio application pauses and freezes, when I try to run my application it run well however when I launch the app on my device it says *unfortunately app has stopped**

Main Java Class File

public class MainActivity extends Activity {
ImageButton btnsignin;
ImageButton btnsignup;

/**
 * Called when the activity is first created.
 */
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    btnsignin = (ImageButton) findViewById(R.id.btnsignin);
    btnsignup = (ImageButton) findViewById(R.id.btnsignup);

    btnsignin.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
            Intent myIntent = new Intent(view.getContext(), Login.class);
            startActivityForResult(myIntent, 0);
            finish();
        }
    });

    btnsignup.setOnClickListener(new View.OnClickListener() {
        public void onClick(View view) {
            Intent myIntent = new Intent(view.getContext(), Register.class);
            startActivityForResult(myIntent, 0);
            finish();
        }
    });
}}

Manifesta file.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.brad.visor" >

    <application
        android:icon="@mipmap/logo"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".Login">
        </activity>
        <activity
            android:name=".Register">
        </activity>
        <activity
            android:name=".Registered">
        </activity>
        <activity
            android:name=".Main">
        </activity>
        <activity
            android:name=".PasswordReset">
        </activity>
        <activity
            android:name=".ChangePassword">
        </activity>

    </application>

    <!-- Allow to connect with internet and to know the current network state-->
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />


</manifest>

LogCat File

Process: com.brad.visor, PID: 13838
    java.lang.RuntimeException: Unable to start activity ComponentInfo{com.brad.visor/com.brad.visor.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2658)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723)
            at android.app.ActivityThread.access$900(ActivityThread.java:172)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:145)
            at android.app.ActivityThread.main(ActivityThread.java:5832)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
     Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ImageButton.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
            at com.brad.visor.MainActivity.onCreate(MainActivity.java:25)
            at android.app.Activity.performCreate(Activity.java:6221)
            at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1119)
            at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2611)
            at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2723)
            at android.app.ActivityThread.access$900(ActivityThread.java:172)
            at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1422)
            at android.os.Handler.dispatchMessage(Handler.java:102)
            at android.os.Looper.loop(Looper.java:145)
            at android.app.ActivityThread.main(ActivityThread.java:5832)
            at java.lang.reflect.Method.invoke(Native Method)
            at java.lang.reflect.Method.invoke(Method.java:372)
            at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
            at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
06-24 21:46:04.285     941-1126/? E/WifiStateMachine﹕ WifiStateMachine CMD_START_SCAN source 10014 txSuccessRate=37.05 rxSuccessRate=33.84 targetRoamBSSID=c4:04:15:c1:13:70 RSSI=-39
06-24 21:46:04.295     941-1126/? E/WifiStateMachine﹕ [1,435,178,764,302 ms] noteScanStartWorkSource{10014} uid 10014
06-24 21:46:07.065      288-288/? E/SMD﹕ DCD ON
06-24 21:46:08.195     941-1126/? E/WifiStateMachine﹕ [1,435,178,768,204 ms] noteScanEnd WorkSource{10014}
06-24 21:46:08.215     941-1126/? E/WifiStateMachine﹕ wifi setScanResults statecom.android.server.wifi.WifiStateMachine$ConnectedState@667b28a sup_state=COMPLETED debouncing=false
06-24 21:46:08.345      941-941/? E/LocSvc_flp﹕ I/===> int flp_inject_location(FlpLocation*) line 222
06-24 21:46:08.345     941-1395/? E/LocSvc_ApiV02﹕ I/<--- void globalRespCb(locClientHandleType, uint32_t, locClientRespIndUnionType, void*) line 125 QMI_LOC_INJECT_POSITION_REQ_V02
06-24 21:46:10.065      288-288/? E/SMD﹕ DCD ON
06-24 21:46:13.066      288-288/? E/SMD﹕ DCD ON
06-24 21:46:16.075      288-288/? E/SMD﹕ DCD ON
06-24 21:46:19.076      288-288/? E/SMD﹕ DCD ON
06-24 21:46:22.075      288-288/? E/SMD﹕ DCD ON
06-24 21:46:25.075      288-288/? E/SMD﹕ DCD ON
06-24 21:46:27.745     941-1334/? E/Watchdog﹕ !@Sync 75
06-24 21:46:28.075      288-288/? E/SMD﹕ DCD ON
06-24 21:46:31.075      288-288/? E/SMD﹕ DCD ON
06-24 21:46:34.075      288-288/? E/SMD﹕ DCD ON
06-24 21:46:37.075      288-288/? E/SMD﹕ DCD ON
06-24 21:46:40.075      288-288/? E/SMD﹕ DCD ON
06-24 21:46:43.075      288-288/? E/SMD﹕ DCD ON
06-24 21:46:46.075      288-288/? E/SMD﹕ DCD ON
06-24 21:46:49.075      288-288/? E/SMD﹕ DCD ON
06-24 21:46:52.075      288-288/? E/SMD﹕ DCD ON
06-24 21:46:55.085      288-288/? E/SMD﹕ DCD ON
06-24 21:46:57.756     941-1334/? E/Watchdog﹕ !@Sync 76
06-24 21:46:58.086      288-288/? E/SMD﹕ DCD ON
06-24 21:47:01.085      288-288/? E/SMD﹕ DCD ON
06-24 21:47:04.085      288-288/? E/SMD﹕ DCD ON
06-24 21:47:05.485     941-1121/? E/Sensors﹕ Acc old sensor_state 0, new sensor_state : 1 en : 1
06-24 21:47:05.505      941-941/? E/LightSensor﹕ Light old sensor_state 1, new sensor_state : 513 en : 1
06-24 21:47:05.515    6462-6462/? E/SPPClientService﹕ [[PushClientService]] F:false, D:false, E:false, T:false, S:true, R:false
06-24 21:47:05.525     941-1126/? E/WifiStateMachine﹕ WifiStateMachine CMD_START_SCAN source 10014 txSuccessRate=37.05 rxSuccessRate=33.84 targetRoamBSSID=c4:04:15:c1:13:70 RSSI=-39
06-24 21:47:05.535     941-1126/? E/WifiStateMachine﹕ [1,435,178,825,536 ms] noteScanStartWorkSource{10014} uid 10014
06-24 21:47:05.765     941-1030/? E/LightSensor﹕ RED : 0, GREEN : 0, BLUE : 0, CLEAR : 0, CALCULATED LUX : 0.000000, CCT : 1596.000000, REAL LUX : 0.000000 a_time = 238, gain = 64, ir=0, rp1=1, gp1=0, bp1=0, cp1=0, cpl=3202560
06-24 21:47:05.765     941-1070/? E/LightSensor﹕ Light old sensor_state 513, new sensor_state : 1 en : 0
06-24 21:47:07.085      288-288/? E/SMD﹕ DCD ON

XML main file

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/linearLayout">

<LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:weightSum="1"
        android:background="#0d47a1">

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:id="@+id/imageView"
            android:src="@drawable/logo"
            android:layout_weight="0.32"
            android:contentDescription="@string/logonew" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:text="@string/logo1"
            android:textColor="#ffffff"
            android:id="@+id/textView"
            android:layout_gravity="center"
            android:textSize="30sp"
            android:layout_marginLeft="25dp" />

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:id="@+id/img_logo"
            android:src="@drawable/logo"
            android:layout_weight="1"
            android:contentDescription="@string/logo2" />



    </LinearLayout>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="122dp"
        android:background="@drawable/bgnew">

        <ImageView
            android:layout_width="match_parent"
            android:layout_height="181dp"
            android:id="@+id/img_mainbanner"
            android:src="@drawable/banner"
            android:background="#64b5f6"
            android:contentDescription="@string/banner" />

    </TableRow>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@drawable/bgnew">

        <ImageView
            android:layout_width="match_parent"
            android:layout_height="181dp"
            android:id="@+id/img_banner2"
            android:src="@drawable/bannernew"
            android:background="#64b5f6"
            android:contentDescription="@string/banner1" />

    </TableRow>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="494dp"
        android:background="#64b5f6"
        android:id="@+id/relativeLayout">

        <ImageButton
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/btnsignin"
            android:background="@android:color/transparent"
            android:layout_alignParentTop="false"
            android:clickable="false"
            android:layout_alignParentBottom="false"
            android:layout_centerHorizontal="true"
            android:src="@drawable/signinbutton" />

        <ImageButton
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/btnsignup"
            android:background="@android:color/transparent"
            android:clickable="false"
            android:layout_centerHorizontal="true"
            android:src="@drawable/signupbutton"
            android:layout_below="@+id/btnsignin" />

        <DigitalClock
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:id="@+id/digitalClock"
            android:textSize="45dp"
            android:textColor="#ffffffff"
            android:layout_below="@+id/btnsignup"
            android:layout_centerHorizontal="true" />

    </RelativeLayout>

</LinearLayout>

Answer 1

Error happens in this line :

btnsignin = (ImageButton) findViewById(R.id.btnsignin);
btnsignin.setOnClickListener(...)

looks like you set incorrect layout or this view (R.id.btnsignin) is not present in him.

Change main.xml layout to :

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:id="@+id/linearLayout">

<LinearLayout
        android:orientation="horizontal"
        android:layout_width="fill_parent"
        android:layout_height="fill_parent"
        android:weightSum="1"
        android:background="#0d47a1">

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:id="@+id/imageView"
            android:src="@drawable/logo"
            android:layout_weight="0.32"
            android:contentDescription="@string/logonew" />

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textAppearance="?android:attr/textAppearanceLarge"
            android:text="@string/logo1"
            android:textColor="#ffffff"
            android:id="@+id/textView"
            android:layout_gravity="center"
            android:textSize="30sp"
            android:layout_marginLeft="25dp" />

        <ImageView
            android:layout_width="wrap_content"
            android:layout_height="match_parent"
            android:id="@+id/img_logo"
            android:src="@drawable/logo"
            android:layout_weight="1"
            android:contentDescription="@string/logo2" />



    </LinearLayout>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="122dp"
        android:background="@drawable/bgnew">

        <ImageView
            android:layout_width="match_parent"
            android:layout_height="181dp"
            android:id="@+id/img_mainbanner"
            android:src="@drawable/banner"
            android:background="#64b5f6"
            android:contentDescription="@string/banner" />

    </TableRow>

    <TableRow
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:background="@drawable/bgnew">

        <ImageView
            android:layout_width="match_parent"
            android:layout_height="181dp"
            android:id="@+id/img_banner2"
            android:src="@drawable/bannernew"
            android:background="#64b5f6"
            android:contentDescription="@string/banner1" />

    </TableRow>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="494dp"
        android:background="#64b5f6"
        android:id="@+id/relativeLayout">

        <ImageButton
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/btnsignin"
            android:background="@android:color/transparent"
            android:layout_alignParentTop="false"
            android:clickable="false"
            android:layout_alignParentBottom="false"
            android:layout_centerHorizontal="true"
            android:src="@drawable/signinbutton" />

        <ImageButton
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/btnsignup"
            android:background="@android:color/transparent"
            android:clickable="false"
            android:layout_centerHorizontal="true"
            android:src="@drawable/signupbutton"
            android:layout_below="@id/btnsignin" />

        <DigitalClock
            android:layout_width="wrap_content"
            android:layout_height="fill_parent"
            android:id="@+id/digitalClock"
            android:textSize="45dp"
            android:textColor="#ffffffff"
            android:layout_below="@id/btnsignup"
            android:layout_centerHorizontal="true" />

    </RelativeLayout>

</LinearLayout>

See this question about the difference between @id and @+id .

Answer 2

在此处输入图像描述任何人都可以帮助我，我的代码中有例外 在此处输入图像描述