Java Can';更新ADT后,为按钮设置onclicklistener
更新ADT后,我真的很沮丧。以前,一个新的Android项目只包括Java Can';更新ADT后,为按钮设置onclicklistener,java,android,adt,Java,Android,Adt,更新ADT后,我真的很沮丧。以前,一个新的Android项目只包括activity\u main.xml文件,我们在其中添加了界面元素。现在,在更新ADT之后,每当我创建一个新的android项目时,它就会创建一个片段\u main.xml以及活动\u main.xml文件。这是什么fragment\u main.xml?还有MainActivity.class包括一些额外的代码,比如名为placeholder fragment的类和一些其他奇怪的东西 现在的主要问题是,我甚至无法为fragme
activity\u main.xml
文件,我们在其中添加了界面元素。现在,在更新ADT之后,每当我创建一个新的android项目时,它就会创建一个片段\u main.xml
以及活动\u main.xml
文件。这是什么fragment\u main.xml
?还有MainActivity.class
包括一些额外的代码,比如名为placeholder fragment
的类和一些其他奇怪的东西
现在的主要问题是,我甚至无法为fragment\u main.xml
中的按钮添加onClickListener
fragment\u 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.example.cameraproject.MainActivity$PlaceholderFragment" >
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="188dp"
android:text="Button" />
</RelativeLayout>
package com.example.cameraproject;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends ActionBarActivity implements OnClickListener {
public static Button b;
@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();
}
b = (Button) findViewById(R.id.button1);
b.setOnClickListener(this);
}
@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;
}
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.button1:
Toast.makeText(this, "Its working", Toast.LENGTH_SHORT).show();
break;
}
}
}
04-22 11:16:54.186: E/AndroidRuntime(17336): FATAL EXCEPTION: main
04-22 11:16:54.186: E/AndroidRuntime(17336): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.cameraproject/com.example.cameraproject.MainActivity}: java.lang.NullPointerException
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2308)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2362)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.ActivityThread.access$700(ActivityThread.java:168)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1329)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.os.Handler.dispatchMessage(Handler.java:99)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.os.Looper.loop(Looper.java:137)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.ActivityThread.main(ActivityThread.java:5493)
04-22 11:16:54.186: E/AndroidRuntime(17336): at java.lang.reflect.Method.invokeNative(Native Method)
04-22 11:16:54.186: E/AndroidRuntime(17336): at java.lang.reflect.Method.invoke(Method.java:525)
04-22 11:16:54.186: E/AndroidRuntime(17336): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1209)
04-22 11:16:54.186: E/AndroidRuntime(17336): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1025)
04-22 11:16:54.186: E/AndroidRuntime(17336): at dalvik.system.NativeStart.main(Native Method)
04-22 11:16:54.186: E/AndroidRuntime(17336): Caused by: java.lang.NullPointerException
04-22 11:16:54.186: E/AndroidRuntime(17336): at com.example.cameraproject.MainActivity.onCreate(MainActivity.java:28)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.Activity.performCreate(Activity.java:5372)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270)
错误日志:
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context="com.example.cameraproject.MainActivity$PlaceholderFragment" >
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:layout_marginTop="188dp"
android:text="Button" />
</RelativeLayout>
package com.example.cameraproject;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v7.app.ActionBarActivity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.Toast;
public class MainActivity extends ActionBarActivity implements OnClickListener {
public static Button b;
@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();
}
b = (Button) findViewById(R.id.button1);
b.setOnClickListener(this);
}
@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;
}
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.button1:
Toast.makeText(this, "Its working", Toast.LENGTH_SHORT).show();
break;
}
}
}
04-22 11:16:54.186: E/AndroidRuntime(17336): FATAL EXCEPTION: main
04-22 11:16:54.186: E/AndroidRuntime(17336): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.cameraproject/com.example.cameraproject.MainActivity}: java.lang.NullPointerException
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2308)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2362)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.ActivityThread.access$700(ActivityThread.java:168)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1329)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.os.Handler.dispatchMessage(Handler.java:99)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.os.Looper.loop(Looper.java:137)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.ActivityThread.main(ActivityThread.java:5493)
04-22 11:16:54.186: E/AndroidRuntime(17336): at java.lang.reflect.Method.invokeNative(Native Method)
04-22 11:16:54.186: E/AndroidRuntime(17336): at java.lang.reflect.Method.invoke(Method.java:525)
04-22 11:16:54.186: E/AndroidRuntime(17336): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1209)
04-22 11:16:54.186: E/AndroidRuntime(17336): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1025)
04-22 11:16:54.186: E/AndroidRuntime(17336): at dalvik.system.NativeStart.main(Native Method)
04-22 11:16:54.186: E/AndroidRuntime(17336): Caused by: java.lang.NullPointerException
04-22 11:16:54.186: E/AndroidRuntime(17336): at com.example.cameraproject.MainActivity.onCreate(MainActivity.java:28)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.Activity.performCreate(Activity.java:5372)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1104)
04-22 11:16:54.186: E/AndroidRuntime(17336): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270)
您已经将布局文件设置为
activity\u main.xml
。但是您已经在fragment\u main.xml
中添加了按钮。这就是引发空指针异常的原因
替换这个
setContentView(R.layout.activity_main);
与
这是最简单的解决方案
或
将fragment\u main.xml
中的全部内容复制到activity\u main.xml
希望有帮助。您已将布局文件设置为
activity\u main.xml
。但您已在fragment\u main.xml
中添加了按钮。这就是引发空指针异常的原因
替换这个
setContentView(R.layout.activity_main);
与
这是最简单的解决方案
或
将fragment\u main.xml
中的全部内容复制到activity\u main.xml
希望对你有帮助试试这个
您的按钮属于fragment\u main.xml
,因此必须在占位符fragment
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
Button b;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
b = (Button) findViewById(R.id.button1);
b.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(getActivity(), "Its working", Toast.LENGTH_SHORT).show();
}
});
return rootView;
}
}
试试这个
您的按钮属于fragment\u main.xml
,因此必须在占位符fragment
public static class PlaceholderFragment extends Fragment {
public PlaceholderFragment() {
}
Button b;
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_main, container, false);
b = (Button) findViewById(R.id.button1);
b.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(getActivity(), "Its working", Toast.LENGTH_SHORT).show();
}
});
return rootView;
}
}
请把这条线放好
setContentView(R.layout.activity\u main)代码>
通过setContentView(R.layout.fragment\u main)代码>重新放置此行
setContentView(R.layout.activity\u main)代码>
通过setContentView(R.layout.fragment\u main)代码>您的按钮属于片段的布局,而不是活动的布局。
因此,从activitie的onCreate()中删除按钮视图初始化代码并添加
View rootView=充气机。充气(R.layout.fragment_main,容器,false);
按钮b=(按钮)rootView.findViewById(R.id.button1)代码>
在占位符片段的onCreateView()中。您的按钮属于片段的布局,而不是活动的布局。
因此,从activitie的onCreate()中删除按钮视图初始化代码并添加
View rootView=充气机。充气(R.layout.fragment_main,容器,false);
按钮b=(按钮)rootView.findViewById(R.id.button1)代码>
在占位符片段的onCreateView()中。谢谢您的回答。但是这个新的片段_main.xml到底是什么。我已经习惯了旧的ADT,它只创建一个activity_main.xml。这个占位符片段是什么东西?@Rakesh你正在创建那个占位符片段。你知道我有什么方法可以恢复到旧式的项目创建。我没有用过这个片段的东西。这是ADT的一个新特性吗?或者我的ADT有问题吗?@Rakesh在你的吐司中将这个改为getActivity()
见我编辑的。谢谢你的回答。但是这个新的片段_main.xml到底是什么。我已经习惯了旧的ADT,它只创建一个activity_main.xml。这个占位符片段是什么东西?@Rakesh你正在创建那个占位符片段。你知道我有什么方法可以恢复到旧式的项目创建。我没有用过这个片段的东西。这是ADT的一个新特性吗?或者我的ADT有问题吗?@Rakesh在你的toast中将这个更改为getActivity()
见我编辑的。这就是我也说过的@lavkushthats我也说过的@lavkushyup那样我就必须更改main activity.class代码,也就是说,从代码中删除那些片段。无论如何,这会奏效的。但我想要的是,无论何时我创建一个新项目,它都不应该包含这个片段_main.xmlseet this@RakeshYa,我以前见过这个线程。我想我必须适应谷歌对ADT的这些新变化。是的,我也建议。。如果我的回答对你有帮助,请接受我的回答@RakeshYup这样我也不得不更改MainActivity.class代码,也就是说,从代码中删除那些片段。无论如何,这样就可以了。但我想要的是,无论何时我创建一个新项目,它都不应该包含这个片段_main.xmlseet this@RakeshYa,我以前见过这个线程。我想我必须适应谷歌对ADT的这些新变化。是的,我也建议。。如果我的回答对你有帮助,请接受我的回答@拉凯什