将文本视图设置为可点击按钮
Setting up a text view as a clickable button
我正在开发一个允许用户使用用户名和密码登录的简单应用程序，我正在尝试以 TextView[= 的形式设置“注册”link 35=] 这会将用户带到应用程序的注册页面。我在我的编码或逻辑中找不到任何错误，但是当我 运行 应用程序并单击注册 link 时，应用程序就关闭了。
这是我的 MainActivity 代码 -
package com.example.squashsademo;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
EditText mTextUsername;
EditText mTextPassword;
Button mButtonLogin;
TextView mTextViewRegister;
// @RequiresApi(api = Build.VERSION_CODES.M)
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextUsername = (EditText)findViewById(R.id.edittext_username);
mTextPassword = (EditText)findViewById(R.id.edittext_password);
mButtonLogin = (Button)findViewById(R.id.button_login);
mTextViewRegister = (TextView)findViewById(R.id.textview_register);
mTextViewRegister.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view){
Intent registerIntent = new Intent(MainActivity.this,RegisterActivity.class);
startActivity(registerIntent);
}
});
}
}
这是我要访问的 RegisterActivity -
package com.example.squashsademo;
import android.content.Intent;
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.TextView;
public class RegisterActivity extends AppCompatActivity {
EditText mTextUsername;
EditText mTextPassword;
EditText mTextCnfPassword;
Button mButtonRegister;
TextView mTextViewLogin;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
mTextUsername = (EditText)findViewById(R.id.edittext_username);
mTextPassword = (EditText)findViewById(R.id.edittext_password);
mTextCnfPassword = (EditText) findViewById(R.id.edittext_cnf_password);
mButtonRegister = (Button)findViewById(R.id.button_login);
mTextViewLogin = (TextView)findViewById(R.id.textview_register);
mTextViewLogin.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view) {
Intent LoginIntent = new Intent(RegisterActivity.this,MainActivity.class);
startActivity(LoginIntent);
}
});
}
}
这是我的 AndroidManifest -
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.squashsademo">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/Theme.SquashSADemo">
<activity android:name=".RegisterActivity"></activity>
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
谁能帮忙看看为什么这不起作用，因为根据我的理解，它应该是:(
谢谢
编辑 - 这里还有布局文件
主要活动-
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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=".MainActivity"
android:orientation="vertical"
android:gravity="center_horizontal"
android:background="@drawable/background">
<ImageView
android:layout_width="299dp"
android:layout_height="80dp"
app:srcCompat="@drawable/logo" />
<EditText
android:id="@+id/edittext_username"
android:layout_width="356dp"
android:layout_height="57dp"
android:layout_marginTop="160dp"
android:background="@drawable/custom_input"
android:drawableLeft="@drawable/username"
android:drawablePadding="12dp"
android:hint="@string/username"
android:textColorHint="@color/white"/>
<EditText
android:id="@+id/edittext_password"
android:layout_width="356dp"
android:layout_height="57dp"
android:layout_marginTop="20dp"
android:background="@drawable/custom_input"
android:drawableLeft="@drawable/password"
android:drawablePadding="12dp"
android:hint="@string/password"
android:textColorHint="@color/white"/>
<Button
android:id="@+id/button_login"
android:layout_width="wrap_content"
android:layout_height="40dp"
android:layout_marginTop="20dp"
android:text="@string/login"/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:layout_width="wrap_content"
android:layout_height="35dp"
android:textColor="#ffffff"
android:text="@string/not_registered"/>
<TextView
android:id="@+id/textview_register"
android:layout_width="wrap_content"
android:layout_height="35dp"
android:paddingLeft="10dp"
android:textStyle="bold"
android:textColor="#ffffff"
android:text="@string/register"/>
</LinearLayout>
</LinearLayout>
RegisterActivity -
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
android:background="@drawable/background"
android:orientation="vertical"
android:gravity="center_horizontal"
tools:context=".RegisterActivity">
<ImageView
android:layout_width="298dp"
android:layout_height="80dp"
app:srcCompat="@drawable/logo" />
<EditText
android:id="@+id/edittext_username"
android:layout_width="356dp"
android:layout_height="57dp"
android:layout_marginTop="160dp"
android:background="@drawable/custom_input"
android:drawableLeft="@drawable/username"
android:drawablePadding="12dp"
android:hint="@string/username"
android:textColorHint="@color/white"/>
<EditText
android:id="@+id/edittext_password"
android:layout_width="356dp"
android:layout_height="57dp"
android:layout_marginTop="20dp"
android:background="@drawable/custom_input"
android:drawableLeft="@drawable/password"
android:drawablePadding="12dp"
android:hint="@string/password"
android:textColorHint="@color/white" />
<EditText
android:id="@+id/edittext_cnf_password"
android:drawablePadding="12dp"
android:background="@drawable/custom_input"
android:layout_width="356dp"
android:layout_height="57dp"
android:layout_marginTop="20dp"
android:drawableLeft="@drawable/password"
android:hint="@string/confirm_password"
android:textColorHint="@color/white"/>
<Button
android:id="@+id/button_register"
android:layout_width="wrap_content"
android:layout_height="40dp"
android:layout_marginTop="20dp"
android:text="@string/register"/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:layout_width="wrap_content"
android:layout_height="35dp"
android:textColor="#ffffff"
android:text="@string/already_registered"/>
<TextView
android:id="@+id/textview_login"
android:layout_width="wrap_content"
android:layout_height="35dp"
android:paddingLeft="10dp"
android:textStyle="bold"
android:textColor="#ffffff"
android:textSize="16dp"
android:text="@string/login"/>
</LinearLayout>
</LinearLayout>
这里还有日志文件 -
2020-10-21 20:56:22.881 11328-11328/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.squashsademo, PID: 11328
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.squashsademo/com.example.squashsademo.RegisterActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3654)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3806)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2267)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:8167)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.squashsademo.RegisterActivity.onCreate(RegisterActivity.java:28)
at android.app.Activity.performCreate(Activity.java:7963)
at android.app.Activity.performCreate(Activity.java:7952)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1307)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3629)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3806)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2267)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:8167)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)
下面的代码行抛出 NullPoinerException
mTextViewLogin = (TextView)findViewById(R.id.textview_register);
在寄存器 activity 布局中，没有 id textview_register 这就是您遇到问题的原因
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
可能使用下面的行修复
mTextViewLogin = (TextView)findViewById(R.id.textview_login);
而不是
mTextViewLogin = (TextView)findViewById(R.id.textview_register);
您可以看到您正在尝试 link XML 使用无效 ID java 查看
我正在开发一个允许用户使用用户名和密码登录的简单应用程序，我正在尝试以 TextView[= 的形式设置“注册”link 35=] 这会将用户带到应用程序的注册页面。我在我的编码或逻辑中找不到任何错误，但是当我 运行 应用程序并单击注册 link 时，应用程序就关闭了。
这是我的 MainActivity 代码 -
package com.example.squashsademo;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
public class MainActivity extends AppCompatActivity {
EditText mTextUsername;
EditText mTextPassword;
Button mButtonLogin;
TextView mTextViewRegister;
// @RequiresApi(api = Build.VERSION_CODES.M)
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextUsername = (EditText)findViewById(R.id.edittext_username);
mTextPassword = (EditText)findViewById(R.id.edittext_password);
mButtonLogin = (Button)findViewById(R.id.button_login);
mTextViewRegister = (TextView)findViewById(R.id.textview_register);
mTextViewRegister.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view){
Intent registerIntent = new Intent(MainActivity.this,RegisterActivity.class);
startActivity(registerIntent);
}
});
}
}
这是我要访问的 RegisterActivity -
package com.example.squashsademo;
import android.content.Intent;
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.TextView;
public class RegisterActivity extends AppCompatActivity {
EditText mTextUsername;
EditText mTextPassword;
EditText mTextCnfPassword;
Button mButtonRegister;
TextView mTextViewLogin;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_register);
mTextUsername = (EditText)findViewById(R.id.edittext_username);
mTextPassword = (EditText)findViewById(R.id.edittext_password);
mTextCnfPassword = (EditText) findViewById(R.id.edittext_cnf_password);
mButtonRegister = (Button)findViewById(R.id.button_login);
mTextViewLogin = (TextView)findViewById(R.id.textview_register);
mTextViewLogin.setOnClickListener(new View.OnClickListener(){
@Override
public void onClick(View view) {
Intent LoginIntent = new Intent(RegisterActivity.this,MainActivity.class);
startActivity(LoginIntent);
}
});
}
}
这是我的 AndroidManifest -
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.example.squashsademo">
<application
android:allowBackup="true"
android:icon="@mipmap/ic_launcher"
android:label="@string/app_name"
android:roundIcon="@mipmap/ic_launcher_round"
android:supportsRtl="true"
android:theme="@style/Theme.SquashSADemo">
<activity android:name=".RegisterActivity"></activity>
<activity android:name=".MainActivity">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
</application>
</manifest>
谁能帮忙看看为什么这不起作用，因为根据我的理解，它应该是:( 谢谢
编辑 - 这里还有布局文件
主要活动-
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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=".MainActivity"
android:orientation="vertical"
android:gravity="center_horizontal"
android:background="@drawable/background">
<ImageView
android:layout_width="299dp"
android:layout_height="80dp"
app:srcCompat="@drawable/logo" />
<EditText
android:id="@+id/edittext_username"
android:layout_width="356dp"
android:layout_height="57dp"
android:layout_marginTop="160dp"
android:background="@drawable/custom_input"
android:drawableLeft="@drawable/username"
android:drawablePadding="12dp"
android:hint="@string/username"
android:textColorHint="@color/white"/>
<EditText
android:id="@+id/edittext_password"
android:layout_width="356dp"
android:layout_height="57dp"
android:layout_marginTop="20dp"
android:background="@drawable/custom_input"
android:drawableLeft="@drawable/password"
android:drawablePadding="12dp"
android:hint="@string/password"
android:textColorHint="@color/white"/>
<Button
android:id="@+id/button_login"
android:layout_width="wrap_content"
android:layout_height="40dp"
android:layout_marginTop="20dp"
android:text="@string/login"/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:layout_width="wrap_content"
android:layout_height="35dp"
android:textColor="#ffffff"
android:text="@string/not_registered"/>
<TextView
android:id="@+id/textview_register"
android:layout_width="wrap_content"
android:layout_height="35dp"
android:paddingLeft="10dp"
android:textStyle="bold"
android:textColor="#ffffff"
android:text="@string/register"/>
</LinearLayout>
</LinearLayout>
RegisterActivity -
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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"
android:background="@drawable/background"
android:orientation="vertical"
android:gravity="center_horizontal"
tools:context=".RegisterActivity">
<ImageView
android:layout_width="298dp"
android:layout_height="80dp"
app:srcCompat="@drawable/logo" />
<EditText
android:id="@+id/edittext_username"
android:layout_width="356dp"
android:layout_height="57dp"
android:layout_marginTop="160dp"
android:background="@drawable/custom_input"
android:drawableLeft="@drawable/username"
android:drawablePadding="12dp"
android:hint="@string/username"
android:textColorHint="@color/white"/>
<EditText
android:id="@+id/edittext_password"
android:layout_width="356dp"
android:layout_height="57dp"
android:layout_marginTop="20dp"
android:background="@drawable/custom_input"
android:drawableLeft="@drawable/password"
android:drawablePadding="12dp"
android:hint="@string/password"
android:textColorHint="@color/white" />
<EditText
android:id="@+id/edittext_cnf_password"
android:drawablePadding="12dp"
android:background="@drawable/custom_input"
android:layout_width="356dp"
android:layout_height="57dp"
android:layout_marginTop="20dp"
android:drawableLeft="@drawable/password"
android:hint="@string/confirm_password"
android:textColorHint="@color/white"/>
<Button
android:id="@+id/button_register"
android:layout_width="wrap_content"
android:layout_height="40dp"
android:layout_marginTop="20dp"
android:text="@string/register"/>
<LinearLayout
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal">
<TextView
android:layout_width="wrap_content"
android:layout_height="35dp"
android:textColor="#ffffff"
android:text="@string/already_registered"/>
<TextView
android:id="@+id/textview_login"
android:layout_width="wrap_content"
android:layout_height="35dp"
android:paddingLeft="10dp"
android:textStyle="bold"
android:textColor="#ffffff"
android:textSize="16dp"
android:text="@string/login"/>
</LinearLayout>
</LinearLayout>
这里还有日志文件 -
2020-10-21 20:56:22.881 11328-11328/? E/AndroidRuntime: FATAL EXCEPTION: main
Process: com.example.squashsademo, PID: 11328
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.squashsademo/com.example.squashsademo.RegisterActivity}: 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:3654)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3806)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2267)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:8167)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
at com.example.squashsademo.RegisterActivity.onCreate(RegisterActivity.java:28)
at android.app.Activity.performCreate(Activity.java:7963)
at android.app.Activity.performCreate(Activity.java:7952)
at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1307)
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3629)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3806)
at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2267)
at android.os.Handler.dispatchMessage(Handler.java:107)
at android.os.Looper.loop(Looper.java:237)
at android.app.ActivityThread.main(ActivityThread.java:8167)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:496)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1100)
下面的代码行抛出 NullPoinerException
mTextViewLogin = (TextView)findViewById(R.id.textview_register);
在寄存器 activity 布局中，没有 id textview_register 这就是您遇到问题的原因
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.TextView.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
可能使用下面的行修复
mTextViewLogin = (TextView)findViewById(R.id.textview_login);
而不是
mTextViewLogin = (TextView)findViewById(R.id.textview_register);
您可以看到您正在尝试 link XML 使用无效 ID java 查看