第五章 Activity的生命周期onCreate和onDestory 2.9

 1 package com.example.activitycircledemo;
 2 
 3 import androidx.annotation.Nullable;
 4 import androidx.appcompat.app.AppCompatActivity;
 5 
 6 import android.content.SharedPreferences;
 7 import android.os.Bundle;
 8 import android.text.TextUtils;
 9 import android.util.Log;
10 import android.view.View;
11 import android.widget.Button;
12 import android.widget.EditText;
13 import android.widget.Toast;
14 
15 public class MainActivity extends AppCompatActivity {
16 
17     private static final String TAG = "MainActivity";
18     private static final String MSG_RECORD = "msg_record";
19     private static final String RECORD_KEY = "msg";
20     private Button mBtnSend;
21     private EditText mEditContent;
22     private SharedPreferences mSharedPreferences;
23 
24     @Override
25     protected void onCreate(Bundle savedInstanceState) {
26         super.onCreate(savedInstanceState);
27         setContentView(R.layout.activity_main);
28 
29         initView();
30 
31         initListener();
32 
33         // 恢复数据,将数据保存在msg_record文件内
34         mSharedPreferences = this.getSharedPreferences(MSG_RECORD, MODE_PRIVATE);
35         String record = mSharedPreferences.getString(RECORD_KEY, null);
36         if (!TextUtils.isEmpty(record)) {
37             mEditContent.setText(record);
38         }
39 
40     }
41 
42     private void initListener() {
43         mBtnSend.setOnClickListener(new View.OnClickListener() {
44             @Override
45             public void onClick(View view) {
46                 // 获取到短信的内容
47                 String content = mEditContent.getText().toString().trim();
48                 if (TextUtils.isEmpty(content)) {
49                     Toast.makeText(MainActivity.this, "内容不能为空", Toast.LENGTH_SHORT).show();
50                     return;
51                 }
52                 Log.d(TAG, "发送短信..." + content);
53             }
54         });
55     }
56 
57     private void initView() {
58         mEditContent = (EditText) this.findViewById(R.id.content);
59         mBtnSend = (Button) this.findViewById(R.id.send);
60     }
61 
62     /**
63      * 用户退出程序后，将已经输入的数据进行保存
64      */
65     @Override
66     protected void onDestroy() {
67         super.onDestroy();
68         // 把数据保存到SharedPreferences
69         String content = mEditContent.getText().toString().trim();
70         if (!TextUtils.isEmpty(content)) {
71             // 取得edit编辑后，将数据通过键值对保存到文件中
72             SharedPreferences.Editor edit = mSharedPreferences.edit();
73             edit.putString(RECORD_KEY, content);
74             edit.commit();
75         }
76 
77     }
78 }

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     xmlns:app="http://schemas.android.com/apk/res-auto"
 4     xmlns:tools="http://schemas.android.com/tools"
 5     android:layout_width="match_parent"
 6     android:layout_height="match_parent"
 7     tools:context=".MainActivity"
 8     android:orientation="vertical">
 9 
10     <EditText
11         android:id="@+id/content"
12         android:layout_width="match_parent"
13         android:layout_height="wrap_content"
14         android:hint="请输入短信内容..."/>
15 
16     <Button
17         android:id="@+id/send"
18         android:layout_width="match_parent"
19         android:layout_height="wrap_content"
20         android:text="发送"/>
21 </LinearLayout>