ODDdaaaaai ODDdaaaaai - 1 month ago 9
Android Question

Implementing ButterKnife giving NullPointer Exception

I'm trying to implement the ButterKnife library in a small project, how ever my app crashes when it starts, details:

here is my MainActivity.java :

package com.example.odai.playwithme;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

import butterknife.BindView;
import butterknife.ButterKnife;

public class MainActivity extends AppCompatActivity {

@BindView(R.id.hello_world) TextView hello;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);

ButterKnife.bind(this);

hello.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(getApplicationContext(), "Hello",
Toast.LENGTH_SHORT).show();
}
});
}
}


my activity_main.xml :

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.odai.playwithme.MainActivity">

<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="Hello World!"
android:id="@+id/hello_world"
android:layout_centerVertical="true"
android:layout_centerHorizontal="true" />
</RelativeLayout>


my build.gradle :

apply plugin: 'com.android.application'

android {
compileSdkVersion 23
buildToolsVersion "23.0.3"

defaultConfig {
applicationId "com.example.odai.playwithme"
minSdkVersion 17
targetSdkVersion 23
versionCode 1
versionName "1.0"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'),
'proguard-rules.pro'
}
}
}

dependencies {
compile fileTree(dir: 'libs', include: ['*.jar'])
testCompile 'junit:junit:4.12'
compile 'com.android.support:appcompat-v7:23.4.0'
compile 'com.jakewharton:butterknife:8.0.1'
}


and this is the error I get whenever I try to run my app :

05-22 20:32:52.019 24076-24076/com.example.odai.playwithme E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.odai.playwithme, PID: 24076
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.odai.playwithme/com.example.odai.playwithme.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2484)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2544)
at android.app.ActivityThread.access$900(ActivityThread.java:150)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1394)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:168)
at android.app.ActivityThread.main(ActivityThread.java:5845)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:797)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:687)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.odai.playwithme.MainActivity.onCreate(MainActivity.java:22)
at android.app.Activity.performCreate(Activity.java:6248)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1125)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2437)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2544) 
at android.app.ActivityThread.access$900(ActivityThread.java:150) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1394) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:168) 
at android.app.ActivityThread.main(ActivityThread.java:5845) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:797) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:687)


any ideas?

Answer

I had this problem a while back, too, and actually just tried again to see if it was just a one time thing. Apparently the newer ButterKnife requires a bit more stuff in your build.gradle:

buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'
    }
}

apply plugin: 'com.neenbedankt.android-apt'

dependencies {
    compile 'com.jakewharton:butterknife:8.0.1'
    apt 'com.jakewharton:butterknife-compiler:8.0.1'
}

(https://github.com/JakeWharton/butterknife)

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