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
　%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>