谈谈Android里的Context的使用
大家好，今天给大家分享一下Android里的Context的一些用法. 这里大致可以分为两种：一是传递Context参数，二是调用全局的Context.
其实我们应用启动的时候会启动Application这个类，这个类是在AndroidManifest.xml文件里其实是默认的
为了让大家更容易理解，写了一个简单的Demo.步骤如下：
第1步：新建一个Android工程ApplicationDemo,目录结构如下：
第2步：新建一个工具类ToolsUtil.java，代码如下
package com.tutor.application;
import android.content.Context;
import android.widget.Toast;
/**
* @author carlshen.
* 应用的一些工具类.
*/
public class ToolUtils {
/**
* 参数带Context.
* @param context
* @param msg
*/
public static void showToast(Context context,String msg){
Toast.makeText(context, msg, Toast.LENGTH_SHORT).show();
}
/**
* 调用全局的Context.
* @param msg
*/
public static void showToast(String msg){
Toast.makeText(MainApplication.getContext(), msg, Toast.LENGTH_SHORT).show();
}
}
第3步：新建一个View命名为MainView.java就是我们Activity现实的View.代码如下：
package com.tutor.application;
import android.app.Activity;
import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.FrameLayout;
/**
* @author carlshen.
* 自定义的MainView.
*/
public class MainView extends FrameLayout implements View.OnClickListener{
private Context mContext;
private Activity mActivity;
/**
* 参数Button.
*/
private Button mArgButton;
/**
* 全局Button.
*/
private Button mGlobleButton;
/**
* 退出Button.
*/
private Button mExitButton;
public MainView(Context context){
super(context);
setupViews();
}
public MainView(Context context, AttributeSet attrs) {
super(context, attrs);
setupViews();
}
private void setupViews(){
//获取View的上下文.
mContext = getContext();
//这里将Context转换为Activity.
mActivity = (Activity)mContext;
LayoutInflater inflater = LayoutInflater.from(mContext);
View v = inflater.inflate(R.layout.main, null);
addView(v);
mArgButton = (Button)v.findViewById(R.id.arg_button);
mGlobleButton = (Button)v.findViewById(R.id.glo_button);
mExitButton = (Button)v.findViewById(R.id.exit_button);
mArgButton.setOnClickListener(this);
mGlobleButton.setOnClickListener(this);
mExitButton.setOnClickListener(this);
}
public void onClick(View v) {
if(v == mArgButton){
ToolUtils.showToast(mContext, "我是通过传递Context参数显示的!");
}else if(v == mGlobleButton){
ToolUtils.showToast("我是通过全局Context显示的!");
}else{
mActivity.finish();
}
}
}
这里MainView.java使用的布局main.xml代码如下：
<?xml version="1.0" encoding="utf-8"?>
第4步：修改ApplicationDemoActivity.java,代码如下：
package com.tutor.application;
import android.app.Activity;
import android.os.Bundle;
public class ApplicationDemoActivity extends Activity {
private static Context aContext;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
MainView mMainView = new MainView(this);
setContentView(mMainView);
aContext = getApplicationContext();
}
/**获取Context.
* @return
*/
public static Context getContext(){
return aContext;
}
}
第5步：运行上述工程效果如下：
文件下载
资源详情
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