我想在我的Android项目中使用 ButterKnife
.
我有 Activity
实现 Interface
. 我正在使用MVP模式 . 我试图从 EditText
获取文本,但它会抛出一个
空指针异常 .
这是我的简单代码 .
Gradle dependencies
compile 'com.jakewharton:butterknife:8.8.1'
Layout
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.example.rao.myapplication.LoginActivity">
<EditText
android:id="@+id/etUseName"
android:layout_width="match_parent"
android:layout_height="wrap_content" />
<EditText
android:id="@+id/etPassword"
android:layout_width="match_parent"
android:layout_height="wrap_content"
app:layout_constraintTop_toBottomOf="@+id/etUseName"/>
<Button
android:id="@+id/btnLogin"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Login"
android:onClick="loginClick"
app:layout_constraintTop_toBottomOf="@+id/etPassword"/>
</android.support.constraint.ConstraintLayout>
Activity
package com.example.rao.myapplication;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import com.example.rao.myapplication.Presenter.LoginActivityPresenter;
import com.example.rao.myapplication.View.LoginActivityView;
import butterknife.BindView;
import butterknife.ButterKnife;
public class LoginActivity extends AppCompatActivity implements LoginActivityView {
@BindView(R.id.etUseName)
EditText userNameET;
@BindView(R.id.etPassword)
EditText passwordET;
@BindView(R.id.btnLogin)
Button loginBtn;
private LoginActivityPresenter presenter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_login);
ButterKnife.bind(this);
passwordET.setText("abcd"); // Fails here as well
presenter = new LoginActivityPresenter(this);
}
@Override
public void navigateToListActivity() {
}
@Override
public void loginFailed() {
}
public void loginClick(View view) {
Toast.makeText(this, userNameET.getText().toString(), Toast.LENGTH_SHORT ).show(); // Fails here
Toast.makeText(this, "test", Toast.LENGTH_SHORT ).show();
}
}
Here is the error log
FATAL EXCEPTION:main进程:com.example.rao.myapplication,PID:24847 java.lang.RuntimeException:无法启动活动ComponentInfo {com.example.rao.myapplication / com.example.rao.myapplication.LoginActivity}:java .lang.NullPointerException:尝试在android上的android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2927)的空对象引用上调用虚方法'void android.widget.EditText.setText(java.lang.CharSequence)' . app.ActivityThread.handleLaunchActivity(ActivityThread.java:2988)位于android.app.Handler上android.app.ActivityThread $ H.handleMessage(ActivityThread.java:1631)的android.app.ActivityThread.-wrap14(ActivityThread.java) . dispatchMessage(Handler.java:102)位于android.app.Looper.loop(Looper.java:154)的android.app.ActivityThread.main(ActivityThread.java:6682),位于java.lang.reflect.Method.invoke(Native方法)在com.android.internal.os.ZygoteInit.main(Zygo)com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:1520) teInit.java:1410)引起:java.lang.NullPointerException:尝试在com.example.rao.myapplication上的空对象引用上调用虚方法'void android.widget.EditText.setText(java.lang.CharSequence)' .LoginActivity.onCreate(LoginActivity.java:34)位于android.app.A.运行中的android.app.Activity.hactCaate.performLaunchActivity上的android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1126)上的android.app.Activity.performCreate(Activity.java:6942) ActivityThread.java:2880)在android.app.A活动中的android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2988)android.app.ActivityThread $ H.handleMessage(ActivityThread.java)的android.app.ActivityThread.-wrap14(ActivityThread.java) 1631)在Android.os.Handler.dispatchMessage(Handler.java:102)的android.app.Looper.loop(Looper.java:154)在android.app.ActivityThread.main(ActivityThread.java:6682)在java . com.android.inter上的com.android.internal.os.ZygoteInit $ MethodAndArgsCaller.run(ZygoteInit.java:1520)中的lang.reflect.Method.invoke(Native Method) nal.os.ZygoteInit.main(ZygoteInit.java:1410)
请你指点我正确的方向 .
2 回答
add below line also in your gradle file....
Hope it solve your problems....
把它放在gradle文件中并检查 . 这是official documentation.的链接
GRADLE