Android开发基础

周正建 發表於 2019-9-21 20:00:00

<h3>Android开发基础</h3>开发基础包括<h3>① Android开发环境搭建</h3><h4>Android Studio的安装</h4>https://developer.android.google.cn/studio/<h4>SDK的下载和配置</h4>两种方法，方法1 拷贝别人的SDK文件夹中的所有内容，放在与AndroidStudio在同级目录方法2 根据Android Studio的向导去下载和安装<h4>模拟器的安装与配置</h4>方法1 拷贝别人的SDK文件夹中的所有内容，放在与AndroidStudio在同级目录方法2 在Android Studio中找到 AVD Manager，根据向导去下载和创建方法3 使用第三方的模拟器，也选择android 4.4版本，比如夜神模拟器3.8(不要用最新的)<h4>注意事项</h4>在下载安装完android studio和sdk之后，创建工程时还会下载gradle工具，用于编译构建目录是：C:\Users\自己的用户名.gradle如果创建工程还有问题，一般做一个小更新就可以。<h3>② Android HelloWorld</h3>Android HelloWorld工程的创建，工程中每一部分的介绍创建工程界面<img src="https://img2018.cnblogs.com/blog/1029347/201909/1029347-20190921195947283-191695100.png">创建完项目之后，产生的文件<img src="https://img2018.cnblogs.com/blog/1029347/201909/1029347-20190921195951716-209055258.png">清单文件<img src="https://img2018.cnblogs.com/blog/1029347/201909/1029347-20190921195956920-1553405823.png"><h3>③ Android 界面开发知识</h3><h4>无形组件：布局的定义与常用属性设置</h4><img src="https://img2018.cnblogs.com/blog/1029347/201909/1029347-20190921200004308-1524687322.png">有形组件：按钮、文件控件、编辑文本、图片控件的定义与常用属性设置指定ID：android:id="@+id/imageView"指定宽度：android:layout_width="wrap_content" android:layout_width="match_parent"wrap_content 内容多大控件就多大，match_parent 匹配父窗口指定高度：android:layout_height="wrap_content"图片控件指定图片源：android:src="@mipmap/ic_launcher" 编辑控件指定提示文本：android:hint="请在此输入密码"按钮控件指定显示文本：android:text="验证"指定控件居中：android:layout_gravity="center"<h4>按钮响应</h4>方法一：设置按钮属性<img src="https://img2018.cnblogs.com/blog/1029347/201909/1029347-20190921200010429-1594397429.png">添加完响应函数后。在函数名上alt+enter实现具体函数内容<pre>public void btnStart1(View view) {         // 启动一个新的activity         // 1. 创建Intent对象         Intent intent = new Intent();         // 2. 设置信息         intent.setClass(this,// 自己                 Main2Activity.class); // 新启动的类的类型     //Main2Activity是新创建的活动界面         // 3. 启动activity         startActivity(intent); //这句包括了三面的3句话的内容     //startActivity(new Intent(this,Main2Activity.class));    }</pre>方法二：先在manifests的Androidmanifest.xml添加<pre><activity android:name=".Main2Activity">             <intent-filter>                             <action android:name="com.bluelesson.action.hello15pb" />                 <category android:name="android.intent.category.DEFAULT" />             </intent-filter>         </activity></pre>action android:name="com.bluelesson.action.hello15pb" 动作的名字category android:name="android.intent.category.DEFAULT" 设置成DEFAULT默认然后调用动作。<pre>    public void btnStart2(View view) {         // 1. 创建Intent对象         Intent intent = new Intent();         // 2. 设置动作         intent.setAction("com.bluelesson.action.hello15pb");         // 3. 启动activity         startActivity(intent);    }</pre>打开服务关闭服务先新建一个服务类用log.d做标签做标注方便观察。<pre>package com.example.mybuttontest; import android.app.Service; import android.content.Intent; import android.os.IBinder; import android.util.Log; public class MyService extends Service {     public MyService() {    }     @Override     public IBinder onBind(Intent intent) {         // TODO: Return the communication channel to the service.         throw new UnsupportedOperationException("Not yet implemented");    }     @Override     public void onCreate() {         super.onCreate();         Log.d("Andy", "onCreate: ");    }     @Override     public void onStart(Intent intent, int startId) {         super.onStart(intent, startId);         Log.d("Andy", "onStart: ");    }     @Override     public int onStartCommand(Intent intent, int flags, int startId) {         Log.d("Andy", "onStartCommand: ");         return super.onStartCommand(intent, flags, startId);    }     @Override     public void onDestroy() {         super.onDestroy();         Log.d("Andy", "onDestroy: ");    } }</pre>再调用它<pre><Button         android:id="@+id/btn3"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:onClick="btnStart3"         android:text="启动一个服务" />     <Button         android:id="@+id/btn4"         android:layout_width="wrap_content"         android:layout_height="wrap_content"         android:onClick="btnStart4"         android:text="关闭服务" /></pre><h3>代码中设置监听器</h3>匿名类直接new接口自动实现接口、内部类实现接口、外部类实现接口① 匿名类直接new接口自动实现接口在MainActivity的重写oncreate函数内<pre>        // 设置按钮响应事件         // 方法1 ：匿名类对象         // 1. 获取按钮对象         Button button2 = findViewById(R.id.btn2);         // 2. 设置监听器         button2.setOnClickListener(new View.OnClickListener() {             //View.OnClickListener会报红，ALT+ENTER可以快速创建下面内容             @Override             public void onClick(View v) {                 Toast toast = Toast.makeText(                         MainActivity.this,// 只要是Context类型的this就行，activity肯定可以，因为其父类的父类。。。是Context                         "按钮2",// 显示的内容                         Toast.LENGTH_SHORT // 显示的时间 LENGTH_SHORT 2秒                );                 toast.show();            }        }); </pre>② 内部类实现接口<pre>// 内部类定义 public class MyOnClickListener implements View.OnClickListener {         @Override         public void onClick(View v) {             Toast toast = Toast.makeText(MainActivity.this,"按钮3",Toast.LENGTH_SHORT ); toast.show();        }    } // 调用         // 获取按钮控件         Button button = findViewById(R.id.button);         // 设置响应监听器         button.setOnClickListener(new MyOnClickListener());</pre>③ 外部类实现接口<pre>public class MainActivity extends AppCompatActivity implements // 方法3：外部类对象         // 1. 获取按钮对象         Button button4 = findViewById(R.id.btn4);         // 2. 设置监听器         button4.setOnClickListener(this);}     @Override     public void onClick(View v) {         Toast toast = Toast.makeText( this,"按钮4",Toast.LENGTH_SHORT); toast.show();}</pre>提示对话框Toast、Dialog的创建与使用<pre>// 弹出信息，自动消失 Toast.makeText(this, // 界面指针                 "显示", // 显示的内容                 Toast.LENGTH_SHORT // 显示的时间 LENGTH_SHORT=2秒         ).show();         // 弹出信息，点击消失         AlertDialog.Builder dlg = new AlertDialog.Builder(this);         dlg.setMessage("内容");         dlg.setTitle("标题");         dlg.show();</pre>④ Android 四大组件Activity,BroadcastReceiver,Service,ContenProivder<ol><li>Activity的生命周期</li></ol>程序运行起来执行：onCreate》onStart》onResume 当activity被覆盖：onPause》onStop当重新显示时：onRestart》onStart》onResume 当关闭时：onPause》onStop》onDestroy<ol start="2"><li>广播接收者的写法</li></ol><h3>IP拨号器</h3>创建广播接收者的子类指定拦截广播的权限(manifest.xml里面添加到包的下一句)<pre><uses‐permission android:name="android.permission.PROCESS_OUTGOING_CALLS"  /></pre>指定拦截广播的动作<pre><receiver             android:name=".MyReceiver"             android:enabled="true"             android:exported="true">             <intent‐filter>                 <action android:name="android.intent.action.NEW_OUTGOING_CALL" />                 <category android:name="android.intent.category.DEFAULT" />             </intent‐filter>         </receiver> </pre>调用<pre>package com.bluelesson.app34_1; import android.content.BroadcastReceiver; import android.content.Context; import android.content.Intent; // 广播接收器，作用是拦截广播，做一些需要做的事情 // 必备条件： // 通过向导新建一个BroadcastReceiver的子类 // 1. 指定权限 // 2. 指定拦截的是哪个广播 // 3. 完成代码 public class MyReceiver extends BroadcastReceiver {     @Override     public void onReceive(Context context, Intent intent) {         // TODO: This method is called when the BroadcastReceiver is receiving         // an Intent broadcast.         //IP拨号器写代码         //1. 获取打电话的号码         String num = getResultData();         // 2. 修改电话号码         setResultData("123456"+num);    } }</pre><h3>开启启动</h3>权限<pre><uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" /></pre>指定拦截广播的动作<pre>        <receiver             android:name=".MyReceiver2"             android:enabled="true"             android:exported="true">             <intent-filter>                 <action android:name="android.intent.action.BOOT_COMPLETED" />                 <category android:name="android.intent.category.DEFAULT" />             </intent-filter>         </receiver></pre>调用<pre>public class MyReceiver2 extends BroadcastReceiver {     @Override     public void onReceive(Context context, Intent intent) {         // TODO: This method is called when the BroadcastReceiver is receiving         // an Intent broadcast.         Log.d("15pb-log", "开机启动");         // 启动activity         //1. 创建Intent         Intent intent1 = new Intent();         // 2. 设置信息         intent1.setClass(context,Main2Activity.class);         intent1.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);// 需要设置标志创建activity栈         // 3. 启动acitivity         context.startActivity(intent1);    } } </pre><h3>服务的生命周期</h3>启动时：onCreate》onStartCommand》onStart 退出时: onDestroy<h3>程序入口</h3><pre>              <application         android:name=".MyApp"</pre>MyApp类<pre>package com.bluelesson.app34_2; import android.app.Application; import android.content.Context; import android.util.Log; public class MyApp extends Application {     // http://androidxref.com/     @Override     protected void attachBaseContext(Context base) {         super.attachBaseContext(base);         Log.d("15pb-log", "MyApp::attachBaseContext");    }     @Override     public void onCreate() {         super.onCreate();         Log.d("15pb-log", "MyApp::onCreate");    } } </pre><h3>⑤ Android 多线程与消息机制</h3>Thread,Handler线程中发消息代码：<pre> // 创建消息对象 Message message = new Message(); message.what = 0x111; message.obj = content; // 发消息给主线程 handler.sendMessage(message); </pre><h3>外部handler创建</h3><h3>网络编程-访问网站-下载图片</h3>权限<pre><uses-permission android:name="android.permission.INTERNET"></uses-permission></pre>消息分发<pre>Handler mHandler = new Handler(){         @Override         public void handleMessage(Message msg) {             super.handleMessage(msg);             //判断对应的消息ID,获取消息内容，设置信息             if(msg.what == SET_TEXT){                 TextView textView = findViewById(R.id.tv1);                 textView.setText((String)msg.obj);            } else if(msg.what == GET_PIC){                 ImageView imageView = findViewById(R.id.iv1);                 imageView.setImageBitmap((Bitmap) msg.obj);            }        }    }; </pre>访问网站<pre> public void onClick(View view) {         // 访问网络的一些注意事项         // 1. 访问网络需要权限         // 2. 访问网络需要在工作线程中操作         // 3. 工作线程中不能操作界面，需要发消息给主线程         // 访问百度         Thread thread = new Thread(){             @Override             public void run() {                 super.run();                 URL url = null;                 try {                     // 1. 创建url对象                     url = new URL("http://www.baidu.com");                     // 2. 打开连接                     HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();                     // 3. 设置信息                     httpURLConnection.setConnectTimeout(2000);                     httpURLConnection.setRequestMethod("GET");                     // 4. 获取返回信息                     // android.os.NetworkOnMainThreadException                     int ret = httpURLConnection.getResponseCode();                     if(ret == 200){                         InputStream inputStream = httpURLConnection.getInputStream();                         ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();                         byte bytes[] = new byte;                         int nReadlen = -1;                         while(true){                             nReadlen = inputStream.read(bytes,0,1024);                             if(nReadlen == -1) break;                             byteArrayOutputStream.write(bytes,0,nReadlen);                        }                         byte bytes1[] = byteArrayOutputStream.toByteArray();                         String s = new String(bytes1);                         Message message = new Message();                         message.what = SET_TEXT;                         message.obj = s;                         mHandler.sendMessage(message);                         // 工作线程中不能有界面操作的 //                       TextView textView = MainActivity.this.findViewById(R.id.tv1); //                       textView.setText(s);                         Log.d("15pb-log", s);                    }                } catch (MalformedURLException e) {                     e.printStackTrace();                } catch (IOException e) {                     e.printStackTrace();                }            }        };         thread.start();    }</pre>下载图片<pre> public void onClick1(View view) {         Thread thread = new Thread(){             @Override             public void run() {                 super.run();                 URL url = null;                 try {                     // 1. 创建url对象                     url = new URL("http://ws4.sinaimg.cn/large/00745YaMly1g76yel1cf6j30u01904qy.jpg");                     // 2. 打开连接                     HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();                     // 3. 设置信息                     httpURLConnection.setConnectTimeout(2000);                     httpURLConnection.setRequestMethod("GET");                     // 4. 获取返回信息                     // android.os.NetworkOnMainThreadException                     int ret = httpURLConnection.getResponseCode();                     if(ret == 200){                         InputStream inputStream = httpURLConnection.getInputStream();                         ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();                         byte bytes[] = new byte;                         int nReadlen = -1;                         while(true){                             nReadlen = inputStream.read(bytes,0,1024);                             if(nReadlen == -1) break;                             byteArrayOutputStream.write(bytes,0,nReadlen);                        }                         byte bytes1[] = byteArrayOutputStream.toByteArray();                         // 将数据转为图片                         Bitmap bitmap = BitmapFactory.decodeByteArray(bytes1,0,bytes1.length);                         Message message = new Message();                         message.what = GET_PIC;                         message.obj = bitmap;                         mHandler.sendMessage(message);                    }                } catch (MalformedURLException e) {                     e.printStackTrace();                } catch (IOException e) {                     e.printStackTrace();                }            }        };         thread.start();    } }</pre>网页要滑动屏幕的话，TextView放在activity_main.xml的ScrollView里面就可以<pre>    <ScrollView         android:layout_width="match_parent"         android:layout_height="wrap_content">         <TextView             android:text="显示内容"             android:id="@+id/tv1"             android:layout_width="match_parent"             android:layout_height="wrap_content" />     </ScrollView> </pre>下载图片。放图片的位置直接用代码就行，注意id最好要重命名。<pre><ImageView         android:id="@+id/iv1"         android:layout_width="match_parent"         android:layout_height="wrap_content" /></pre> 
来源：https://www.cnblogs.com/ltyandy/p/11564388.html

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Android开发基础