Butterknife - 空指針異常

我在學習Butterknife，下面是我的簡單示例代碼。但是當我運行時，它會拋出NullPointerException在「setText」。它是Android的工作室的錯誤，因爲我在很多論壇上閱讀還是我的編碼是錯誤的Butterknife - 空指針異常

public class MainActivity extends AppCompatActivity { 

    @Inject 
    SharedPreferences mSharedPrefs; 
    @BindView(R.id.txtName) EditText entervalue; 
    @BindView(R.id.enternamelabel) TextView enternamelabel; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main); 

     //Call Butterknife 
     ButterKnife.bind(MainActivity.this); 

     enternamelabel.setText("Enter Name"); 

     //((DemoApplication) getApplication()).getComponent().inject(this); 
     //mSharedPrefs.edit().putString("status", "success!").apply(); 

    }

APP模塊

apply plugin: 'com.android.application' 
apply plugin: 'com.neenbedankt.android-apt' //For Butterknife 

android { 
    compileSdkVersion 25 
    buildToolsVersion "25.0.3" 
    defaultConfig { 
     applicationId "com.myandroidframework.myandroidframework" 
     minSdkVersion 15 
     targetSdkVersion 25 
     versionCode 1 
     versionName "1.0" 
     testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner" 
     compileOptions.incremental = false 
    } 
    buildTypes { 
     release { 
      minifyEnabled false 
      proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro' 
     } 
    } 
} 

dependencies { 
    compile fileTree(dir: 'libs', include: ['*.jar']) 
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', { 
     exclude group: 'com.android.support', module: 'support-annotations' 
    }) 
    compile 'com.android.support:appcompat-v7:25.3.1' 
    compile 'com.android.support.constraint:constraint-layout:1.0.2' 
    testCompile 'junit:junit:4.12' 

    // Dependency Injection - Dagger2 
    compile 'com.google.dagger:dagger:2.0' 
    provided 'com.google.dagger:dagger-compiler:2.0' 
    provided 'org.glassfish:javax.annotation:10.0-b28' 

    // Dependency Injection - Butterknife 
    testCompile 'junit:junit:4.12' 
    compile 'com.jakewharton:butterknife:8.5.1' 
    annotationProcessor 'com.jakewharton:butterknife-compiler:8.5.1' 
}

項目模塊

// Top-level build file where you can add configuration options common to all sub-projects/modules. 

buildscript { 
    repositories { 
     jcenter() 
    } 
    dependencies { 
     classpath 'com.android.tools.build:gradle:2.3.2' 
     //For Butterknife 
     classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8' 

    } 
} 

allprojects { 
    repositories { 
     jcenter() 
    } 
} 

task clean(type: Delete) { 
    delete rootProject.buildDir 
}

錯誤：

07-19 16:11:22.422 21754-21754/? E/AndroidRuntime: FATAL EXCEPTION: main 
                Process: com.myandroidframework.myandroidframework, PID: 21754 
                java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myandroidframework.myandroidframework/com.myandroidframework.myandroidframework.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference 
                 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2665) 
                 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726) 
                 at android.app.ActivityThread.-wrap12(ActivityThread.java) 
                 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477) 
                 at android.os.Handler.dispatchMessage(Handler.java:102) 
                 at android.os.Looper.loop(Looper.java:154) 
                 at android.app.ActivityThread.main(ActivityThread.java:6119) 
                 at java.lang.reflect.Method.invoke(Native Method) 
                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 
                Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setText(java.lang.CharSequence)' on a null object reference 
                 at com.myandroidframework.myandroidframework.MainActivity.onCreate(MainActivity.java:37) 
                 at android.app.Activity.performCreate(Activity.java:6679) 
                 at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1118) 
                 at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2618) 
                 at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2726)  
                 at android.app.ActivityThread.-wrap12(ActivityThread.java)  
                 at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1477)  
                 at android.os.Handler.dispatchMessage(Handler.java:102)  
                 at android.os.Looper.loop(Looper.java:154)  
                 at android.app.ActivityThread.main(ActivityThread.java:6119)  
                 at java.lang.reflect.Method.invoke(Native Method)  
                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)  
                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)

來源

2017-07-19 user45678

發表您的日誌在這裏 –

@SunilP - 編輯和發佈 – user45678

沒有ü檢查TextView的ID給出正確的嗎？ –

這裏是問題

我不需要加入這行

apply plugin: 'com.jakewharton.butterknife'

下面將我的應用程序級gradle這個

// Dependency Injection - Butterknife 
    testCompile 'junit:junit:4.12' 
    compile 'com.jakewharton:butterknife:8.5.1' 
    annotationProcessor 'com.jakewharton:butterknife-compiler:8.5.1' 
}

下面將我的項目水平gradle這個

dependencies { 
     classpath 'com.android.tools.build:gradle:2.3.2' 
     //For Butterknife 
     classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8' 

    }

來源

2017-07-20 06:19:13 user45678

這個答案並不完全問題，仍然出現錯誤：找不到id爲'com.jakewharton.butterknife'的插件。 – Light

應用級（的build.gradle）

apply plugin: 'android-apt' 
dependencies { 
    compile fileTree(include: ['*.jar'], dir: 'libs') 
    compile 'com.android.support:appcompat-v7:24.2.1' 
    testCompile 'junit:junit:4.12' 
    compile 'com.jakewharton:butterknife:8.4.0' 
    apt 'com.jakewharton:butterknife-compiler:8.4.0' 
} 


Project Level(build.gradle) 

buildscript { 
    repositories { 
     jcenter() 
    } 
    dependencies { 

     classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8' 
     // NOTE: Do not place your application dependencies here; they belong 
     // in the individual module build.gradle files 
    } 
}

來源

2017-11-20 05:53:01 Ashutosh

Butterknife - 空指針異常

回答

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