Question

这是AndroidManifest.XML

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

<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/AppTheme">
    <activity android:name=".FirstActivity"
        android:label="This is FirstActivity">
        <intent-filter>
            <action android:name="android.intent.action.MAIN"/>
            <category android:name="android.intent.category.LAUNCHER"/>
        </intent-filter>
    </activity>
</application>

这是FirstActivity.java

package activitytest.example.com.activitytest;

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

public class FirstActivity extends AppCompatActivity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.first_layout);
    Button button1 = (Button) findViewById(R.id.button_1);
    button1.setOnClickListener(new View.OnClickListener(){
        @Override
        public void onClick(View v){
            Toast.makeText(FirstActivity.this,"You clicked Button 1",
                    Toast.LENGTH_SHORT).show();
        }
    });
}
}

错误就在于此：

Button button1 = (Button) findViewById(R.id.button_1);

无法找到Button类，我该如何解决？这是fisrt_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent">
<Button
    android:id="@+id/button_1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Button_1" />

这是我第一次学习Android，请帮帮我。谢谢。

Answer 1

import android.widget.Button课程中没有FirstActivity。

Answer 2

这是因为您必须在Activity课程中添加导入行。添加以下行：

import android.widget.Button

Android Studio无法找到类Button

2 个答案: