java - setOnclicklistener 方法不起作用

Question

因此，每当我尝试使用 set onclicklistener 并尝试在模拟器上运行它时，它都会显示一条错误消息，指出应用程序已停止。当我取出那部分代码时，它开始工作。

这是我的代码:(Mainactivity.java 文件)

package com.example.android_project_thenewboston;


  import android.support.v7.app.ActionBarActivity;
  import android.support.v7.app.ActionBar;
  import android.support.v4.app.Fragment;
  import android.os.Bundle;
  import android.view.LayoutInflater;
  import android.view.Menu;
  import android.view.MenuItem;
  import android.view.View;
  import android.view.ViewGroup;
  import android.os.Build;
  import android.widget.Button;
  import android.widget.TextView;

  public class MainActivity extends ActionBarActivity {
int counter;
Button add, sub;
TextView display;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    counter = 0;
        add = (Button) findViewById(R.id.bAdd);
        sub = (Button) findViewById(R.id.bSub);
        display = (TextView) findViewById(R.id.tDisplay);
        add.setOnClickListener(new View.OnClickListener() {


            public void onClick(View v) {
                // TODO Auto-generated method stub
                counter++;
                display.setText("Your grand total is " +counter);
            }
        });
        sub.setOnClickListener(new View.OnClickListener() {


            public void onClick(View v) {
                // TODO Auto-generated method stub
                counter--;
                display.setText("Your grand total is " +counter);
            }
        });
    if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction()
                .add(R.id.container, new               PlaceholderFragment()).commit();
    }

}




@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) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();
    if (id == R.id.action_settings) {
        return true;
    }
    return super.onOptionsItemSelected(item);
}

/**
 * A placeholder fragment containing a simple view.
 */
public static class PlaceholderFragment extends Fragment {

    public PlaceholderFragment() {
    }

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container,
                false);
        return rootView;
    }
}

}

____________________________________________________________________________________
fragment_main.xml


<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:orientation = "vertical"
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.android_project_thenewboston.MainActivity$PlaceholderFragment" >

<TextView
    android:id="@+id/textView1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:text="My name is shiven"
    android:textSize="30dp" />
<TextView
    android:id = "@+id/text1"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:text=""
    android:textSize="10dp" />
<Button
    android:id ="@+id/bAdd"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:text="Add one"
    android:textColor="#FFFFFFFF"
    android:textSize="30dp" />
<TextView
    android:id = "@+id/tDisplay"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:text=""
    android:textSize="10dp" />
 <Button

    android:id = "@+id/bSub"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:gravity="center"
    android:text="Subtract one"
    android:textColor="#FFFFFFFF"
    android:textSize="30dp"/>

Answer 1

我认为你的问题是你的按钮位于 fragment 布局中，而不是位于主要 Activity xml 布局中。

onClickListener 代码应放置在 fragment 代码内。

例如:

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
        Bundle savedInstanceState) {
    View rootView = inflater.inflate(R.layout.fragment_main, container,
            false);

    add = (Button) rootView.findViewById(R.id.bAdd);
    sub = (Button) rootView.findViewById(R.id.bSub);
    display = (TextView) rootView.findViewById(R.id.tDisplay);
    add.setOnClickListener(new View.OnClickListener() {


        public void onClick(View v) {
            // TODO Auto-generated method stub
            counter++;
            display.setText("Your grand total is " +counter);
        }
    });
    return rootView;
}

此外，请添加您的代码和 xml/logcat 崩溃输出。