Android 开发笔记___Application操作全局变量

只要app在运行中，他就是一个application。因此可以用它来保存一些全局变量

 package com.example.alimjan.hello_world;

 import android.app.Application;

 import java.util.HashMap;

 /**
  * Created by alimjan on 7/5/2017.
  */

         import android.graphics.Bitmap;
         import android.util.Log;

 public class MainApplication extends Application {

     private final static String TAG = "MainApplication";
     private static MainApplication mApp;
     public HashMap<String, String> mInfoMap = new HashMap<String, String>();

     public static MainApplication getInstance() {
         return mApp;
     }

     @Override
     public void onCreate() {
         super.onCreate();
         mApp = this;
         Log.d(TAG, "onCreate");
     }

     @Override
     public void onTerminate() {
         Log.d(TAG, "onTerminate");
         super.onTerminate();
     }

     public HashMap<Long, Bitmap> mIconMap = new HashMap<Long, Bitmap>();

 }

write

 package com.example.alimjan.hello_world;

 /**
  * Created by alimjan on 7/5/2017.
  */

         import android.content.Context;
         import android.content.Intent;
         import android.os.Bundle;
         import android.support.v7.app.AppCompatActivity;
         import android.view.View;
         import android.view.View.OnClickListener;
         import android.widget.AdapterView;
         import android.widget.ArrayAdapter;
         import android.widget.EditText;
         import android.widget.Spinner;
         import android.widget.Toast;
         import android.widget.AdapterView.OnItemSelectedListener;
         import com.example.alimjan.hello_world.Utils.DateUtil;

 public class class_4_4_2 extends AppCompatActivity implements OnClickListener {

     private EditText et_name;
     private EditText et_age;
     private EditText et_height;
     private EditText et_weight;
     private boolean bMarried = false;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.code_4_4_2);
         et_name = (EditText) findViewById(R.id.et_name);
         et_age = (EditText) findViewById(R.id.et_age);
         et_height = (EditText) findViewById(R.id.et_height);
         et_weight = (EditText) findViewById(R.id.et_weight);
         findViewById(R.id.btn_save).setOnClickListener(this);

         ArrayAdapter<String> typeAdapter = new ArrayAdapter<String>(this,
                 R.layout.item_select, typeArray);
         typeAdapter.setDropDownViewResource(R.layout.item_dropdown);
         Spinner sp_married = (Spinner) findViewById(R.id.sp_married);
         sp_married.setPrompt("请选择婚姻状况");
         sp_married.setAdapter(typeAdapter);
         sp_married.setSelection(0);
         sp_married.setOnItemSelectedListener(new TypeSelectedListener());
     }

     private String[] typeArray = {"未婚", "已婚"};
     class TypeSelectedListener implements OnItemSelectedListener {
         public void onItemSelected(AdapterView<?> arg0, View arg1, int arg2, long arg3) {
             bMarried = (arg2==0)?false:true;
         }

         public void onNothingSelected(AdapterView<?> arg0) {
         }
     }

     @Override
     public void onClick(View v) {
         if (v.getId() == R.id.btn_save) {
             String name = et_name.getText().toString();
             String age = et_age.getText().toString();
             String height = et_height.getText().toString();
             String weight = et_weight.getText().toString();
             if (name==null || name.length()<=0) {
                 showToast("请先填写姓名");
                 return;
             }
             if (age==null || age.length()<=0) {
                 showToast("请先填写年龄");
                 return;
             }
             if (height==null || height.length()<=0) {
                 showToast("请先填写身高");
                 return;
             }
             if (weight==null || weight.length()<=0) {
                 showToast("请先填写体重");
                 return;
             }

             MainApplication app = MainApplication.getInstance();
             app.mInfoMap.put("name", name);
             app.mInfoMap.put("age", age);
             app.mInfoMap.put("height", height);
             app.mInfoMap.put("weight", weight);
             app.mInfoMap.put("married", typeArray[bMarried==false?0:1]);
             app.mInfoMap.put("update_time", DateUtil.getCurDateStr("yyyy-MM-dd HH:mm:ss"));
             showToast("数据已写入全局内存");
         }
     }

     private void showToast(String desc) {
         Toast.makeText(this, desc, Toast.LENGTH_SHORT).show();
     }

     public static void startHome(Context mcontext){
         Intent intent = new Intent(mcontext,class_4_4_2.class);
         mcontext.startActivity(intent);
     }

 }

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:focusable="true"
     android:focusableInTouchMode="true"
     android:orientation="vertical"
     android:padding="10dp" >

     <RelativeLayout
         android:layout_width="match_parent"
         android:layout_height="50dp" >

         <TextView
             android:id="@+id/tv_name"
             android:layout_width="wrap_content"
             android:layout_height="match_parent"
             android:layout_alignParentLeft="true"
             android:gravity="center"
             android:text="姓名："
             android:textColor="@color/black"
             android:textSize="17sp" />

         <EditText
             android:id="@+id/et_name"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             android:layout_marginBottom="5dp"
             android:layout_marginTop="5dp"
             android:layout_toRightOf="@+id/tv_name"
             android:background="@drawable/editext_selector"
             android:gravity="left|center"
             android:hint="请输入姓名"
             android:inputType="text"
             android:maxLength="12"
             android:textColor="@color/black"
             android:textColorHint="@color/grey"
             android:textCursorDrawable="@drawable/text_cursor"
             android:textSize="17sp" />
     </RelativeLayout>

     <RelativeLayout
         android:layout_width="match_parent"
         android:layout_height="50dp" >

         <TextView
             android:id="@+id/tv_age"
             android:layout_width="wrap_content"
             android:layout_height="match_parent"
             android:layout_alignParentLeft="true"
             android:gravity="center"
             android:text="年龄："
             android:textColor="@color/black"
             android:textSize="17sp" />

         <EditText
             android:id="@+id/et_age"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             android:layout_marginBottom="5dp"
             android:layout_marginTop="5dp"
             android:layout_toRightOf="@+id/tv_age"
             android:background="@drawable/editext_selector"
             android:gravity="left|center"
             android:hint="请输入年龄"
             android:inputType="number"
             android:maxLength="2"
             android:textColor="@color/black"
             android:textColorHint="@color/grey"
             android:textCursorDrawable="@drawable/text_cursor"
             android:textSize="17sp" />
     </RelativeLayout>

     <RelativeLayout
         android:layout_width="match_parent"
         android:layout_height="50dp" >

         <TextView
             android:id="@+id/tv_height"
             android:layout_width="wrap_content"
             android:layout_height="match_parent"
             android:layout_alignParentLeft="true"
             android:gravity="center"
             android:text="身高："
             android:textColor="@color/black"
             android:textSize="17sp" />

         <EditText
             android:id="@+id/et_height"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             android:layout_marginBottom="5dp"
             android:layout_marginTop="5dp"
             android:layout_toRightOf="@+id/tv_height"
             android:background="@drawable/editext_selector"
             android:gravity="left|center"
             android:hint="请输入身高"
             android:inputType="number"
             android:maxLength="3"
             android:textColor="@color/black"
             android:textColorHint="@color/grey"
             android:textCursorDrawable="@drawable/text_cursor"
             android:textSize="17sp" />
     </RelativeLayout>

     <RelativeLayout
         android:layout_width="match_parent"
         android:layout_height="50dp" >

         <TextView
             android:id="@+id/tv_weight"
             android:layout_width="wrap_content"
             android:layout_height="match_parent"
             android:layout_alignParentLeft="true"
             android:gravity="center"
             android:text="体重："
             android:textColor="@color/black"
             android:textSize="17sp" />

         <EditText
             android:id="@+id/et_weight"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             android:layout_marginBottom="5dp"
             android:layout_marginTop="5dp"
             android:layout_toRightOf="@+id/tv_weight"
             android:background="@drawable/editext_selector"
             android:gravity="left|center"
             android:hint="请输入体重"
             android:inputType="numberDecimal"
             android:maxLength="5"
             android:textColor="@color/black"
             android:textColorHint="@color/grey"
             android:textCursorDrawable="@drawable/text_cursor"
             android:textSize="17sp" />
     </RelativeLayout>

     <RelativeLayout
         android:layout_width="match_parent"
         android:layout_height="50dp" >

         <TextView
             android:id="@+id/tv_married"
             android:layout_width="wrap_content"
             android:layout_height="match_parent"
             android:layout_alignParentLeft="true"
             android:gravity="center"
             android:text="婚否："
             android:textColor="@color/black"
             android:textSize="17sp" />

         <Spinner
             android:id="@+id/sp_married"
             android:layout_width="match_parent"
             android:layout_height="match_parent"
             android:layout_toRightOf="@+id/tv_married"
             android:gravity="left|center"
             android:spinnerMode="dialog" />
     </RelativeLayout>

     <Button
         android:id="@+id/btn_save"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:text="保存到全局内存"
         android:textColor="@color/black"
         android:textSize="20sp" />

 </LinearLayout>

read

 package com.example.alimjan.hello_world;

 import java.util.Map;

 /**
  * Created by alimjan on 7/5/2017.
  */

 import android.content.Context;
 import android.content.Intent;
 import android.os.Bundle;
         import android.support.v7.app.AppCompatActivity;
         import android.widget.TextView;

 public class class_4_4_2_1 extends AppCompatActivity {

     private TextView tv_app;

     @Override
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         setContentView(R.layout.code_4_4_2_1);
         tv_app = (TextView) findViewById(R.id.tv_app);
         readAppMemory();
     }

     private void readAppMemory() {
         String desc = "全局内存中保存的信息如下：";
         MainApplication app = MainApplication.getInstance();
         Map<String, String> mapParam = app.mInfoMap;
         for (Map.Entry<String, String> item_map : mapParam.entrySet()) {
             desc = String.format("%s\n　%s的取值为%s",
                     desc, item_map.getKey(), item_map.getValue());
         }
         if (mapParam==null || mapParam.size()<=0) {
             desc = "全局内存中保存的信息为空";
         }
         tv_app.setText(desc);
     }

     public static void startHome(Context mcontext){
         Intent intent = new Intent(mcontext,class_4_4_2_1.class);
         mcontext.startActivity(intent);
     }

 }

 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="match_parent"
     android:focusable="true"
     android:focusableInTouchMode="true"
     android:orientation="vertical"
     android:padding="10dp" >

     <TextView
         android:id="@+id/tv_app"
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:textColor="@color/black"
         android:textSize="17sp" />

 </LinearLayout>