Android Studio 中的 OnClickListener

Question

我正在尝试使用新的 Android Studio 进行开发和应用，但我的 OnClickListeners 不断收到重大错误。主要是告诉我它无法解析符号“setOnClickListener”，也无法解析“View v”

package com.sigmachi.derbydays;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {

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


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    Button button= (Button) findViewById(R.id.standingsButton);
    button.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            startActivity(new Intent(MainActivity.this,StandingsActivity.class));
        }
    });

那是类中的代码

Information:Compilation completed with 11 errors and 0 warnings in 4 sec
Information:11 errors
Information:0 warnings
/Users/angelo/AndroidStudioProjects/SigmaChiDerbyDaysProject/SigmaChiDerbyDays/src/main/java/com/sigmachi/derbydays/MainActivity.java
    Error:Error:line (28)Gradle: <identifier> expected
    Error:Error:line (28)Gradle: illegal start of type
    Error:Error:line (28)Gradle: ')' expected
    Error:Error:line (28)Gradle: ';' expected
    Error:Error:line (28)Gradle: invalid method declaration; return type required
    Error:Error:line (30)Gradle: illegal start of type
    Error:Error:line (30)Gradle: ';' expected
    Error:Error:line (30)Gradle: ')' expected
    Error:Error:line (30)Gradle: not a statement
    Error:Error:line (30)Gradle: ';' expected
    Error:Error:line (33)Gradle: illegal start of type

这些是我收到的完全没有意义的错误。第 28 行从我做button.setOnClickListener时开始

编辑：现在当我按下按钮时，我会收到强制关闭

这是它应该打开的类，一个裸类，唯一的变化是要打开的布局

package com.sigmachi.derbydays;

import android.os.Bundle;
import android.app.Activity;
import android.view.Menu;

public class StandingsActivity extends Activity {

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


    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

}

Answer 1

Button button= (Button) findViewById(R.id.standingsButton);
button.setOnClickListener(new View.OnClickListener() {
    public void onClick(View v) {
        startActivity(new Intent(MainActivity.this,StandingsActivity.class));
    }
});

此代码不在任何方法中。如果你想使用它，它必须在OnCreate()之类的方法中

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

    Button button= (Button) findViewById(R.id.standingsButton);
    button.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            startActivity(new Intent(MainActivity.this,StandingsActivity.class));
        }
    });
}

Answer 2

您将需要在方法内按按钮初始化，而不是尝试在类级别初始化视图：

 Button button;  //<< declare here..

   @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        button= (Button) findViewById(R.id.standingsButton); //<< initialize here
         // set OnClickListener for Button here
        button.setOnClickListener(new View.OnClickListener() {
        public void onClick(View v) {
            startActivity(new Intent(MainActivity.this,StandingsActivity.class));
        }
      });
    }

Answer 3

这对我有用：

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_newarea);

    btnSave = (Button)findViewById(R.id.btnSave);

    OnClickListener btnListener = new OnClickListener() {
        @Override
        public void onClick(android.view.View view) {
            finish();
        }
    };
    btnSave.setOnClickListener(btnListener);

}

Answer 4

protected void onCreate(Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_my);
    titolorecuperato = (TextView) findViewById(R.id.textView);
    String stitolo = titolorecuperato.getText().toString();

    Button btnHome = (Button) findViewById(R.id.button);

    btnHome.setOnClickListener(new View.OnClickListener() {

       @Override
        public void onClick(View view) {

       }
});

和 Nic007 之前说的一样。

您确实需要在“onCreate”方法中编写代码。也对不起我的缩进...（这里的第一条评论）

Answer 5

@Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

 @Override
    public boolean onOptionsItemSelected(MenuItem item) {
         int id = item.getItemId();
         if (id == R.id.standingsButton) {
            startActivity(new Intent(MainActivity.this,StandingsActivity.class));
            return true;
        }
        return super.onOptionsItemSelected(item);
    }