按钮无法在Android应用中使用

时间：2016-09-02 09:43:10

标签： java android eclipse

我是java编程的新手，我关注了一些关于JAVA的书。我用eclipse。

我正在处理一个简单的程序，但按钮的功能不能很好，这是我的代码

MainActivity.java 

import android.support.v7.app.ActionBarActivity;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;

import android.view.View;
import android.view.ViewGroup;


public class MainActivity extends ActionBarActivity {

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

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment())
                    .commit();
        }
    } 

    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);
            Button b = (Button) rootView.findViewById(R.id.button1);
            b.setOnClickListener(new OnClickListener(){
                public void onClick(View v){
                    getActivity().startActivity(new Intent(Main.this, Recipe.class));
                }
            });
            return rootView;
        }
    }

}

Recipe.java 

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;

public class Recipe extends ActionBarActivity {

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

activity_main.xml中

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/container"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.helloandroidword.MainActivity"
    tools:ignore="MergeRootFrame" />

fragment_main.xml 

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:tools="http://schemas.android.com/tools"
        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.helloandroidword.MainActivity$PlaceholderFragment" >

        <TextView
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@string/hello_world" />

        <Button
            android:id="@+id/btnRecipe"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_alignParentRight="true"
            android:layout_alignParentTop="true"
            android:layout_marginRight="20dp"
            android:text="Button" />

    </RelativeLayout>

AndroidManifest 

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.helloandroidword"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="8"
        android:targetSdkVersion="19" />

    <application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name="com.helloandroidword.MainActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity android:name=".Recipe"/>
    </application>

</manifest>

感谢

5 个答案:

答案 0 :(得分：2)

您编写了自己的findViewById(int btnrecipe)，它始终返回null：

private Button findViewById(int btnrecipe) {
    // TODO Auto-generated method stub
    return null;
}

您应该从活动中调用findViewById。

答案 1 :(得分：1)

您需要使用Intent进入下一个屏幕（活动）。

在onClickListener中添加以下代码中的一件事。

Intent intent = new Intent(activity.this, recipe.class); startActivity(intent);

答案 2 :(得分：1)

在活动课程中，您使用extend

Activity

public class activity

更改为

public class activity extends Activity

答案 3 :(得分：1)

将activity重命名为MyActivity以保持标准命名约定。

您的activity课程应该如下所示，

public class MyActivity extends Activity {

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

        Button b = (Button) findViewById(R.id.btnRecipe);
        b.setOnClickListener(new OnClickListener(){
            @Override
            public void onClick(View arg0) {
                Intent intent = new Intent(MyActivity.this, recipe.class);
                startActivity(intent);
            }
        });

    }

}

同样在recipe班级变更中，

public class recipe extends MainActivity

要，

public class recipe extends Activity

在你的舱单变更中，

<activity-alias android:name=".recipe"/>

要，

<activity android:name=".recipe"/>

答案 4 :(得分：0)

非常感谢K Neeraj Lal的特别感谢...请按照代码进行操作。 MainActivity.java 

import android.support.v7.app.ActionBarActivity;
import android.support.v4.app.Fragment;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;


public class MainActivity extends ActionBarActivity {

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

        if (savedInstanceState == null) {
            getSupportFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment())
                    .commit();
        }
    }




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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
        View rootView = inflater.inflate(R.layout.fragment_main, container, false);
        Button b = (Button) rootView.findViewById(R.id.button1);
        b.setOnClickListener(new OnClickListener(){
            public void onClick(View v){
                startActivity(new Intent(getActivity(), Recipe.class));


            }


        });
    return rootView;
    }
}

}

Recipe.java 

    import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.support.v4.app.Fragment;
import android.os.Build;

public class Recipe extends ActionBarActivity  {
    @Override
    protected void onCreate(Bundle savedInstanceState){ 

     super.onCreate(savedInstanceState);
     setContentView(R.layout.recipe);

    }
}

activity_main.xml中

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="net.androidbootcamp.healthyrecipes.MainActivity"
tools:ignore="MergeRootFrame" />

fragment_main.xml 

    <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    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="net.androidbootcamp.healthyrecipes.MainActivity$PlaceholderFragment" >

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="clic"/>

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_above="@+id/button1"
        android:layout_centerHorizontal="true"
        android:layout_marginBottom="47dp"
        android:src="@drawable/ic_launcher" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/button1"
        android:layout_alignParentTop="true"
        android:layout_marginTop="16dp"
        android:text="@string/hello_world"
        android:textSize="20sp" />

</RelativeLayout>

recipe.xml 

    <?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="91dp"
        android:layout_marginTop="45dp"
        android:text="Large Text"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/textView1"
        android:layout_marginLeft="43dp"
        android:layout_marginTop="45dp"
        android:text="pomodori"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView2"
        android:layout_below="@+id/textView2"
        android:layout_marginTop="30dp"
        android:text="acqua"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textView4"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView3"
        android:layout_centerVertical="true"
        android:text="sale"
        android:textAppearance="?android:attr/textAppearanceMedium" />

    <TextView
        android:id="@+id/textView5"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView4"
        android:layout_below="@+id/textView4"
        android:layout_marginTop="37dp"
        android:text="pepe"
        android:textAppearance="?android:attr/textAppearanceMedium" />

</RelativeLayout>
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