Android Training: 创建第一个APP

搭建环境

1. 下载 Android Studio
2. 下载 SDK tools SDK Manager

创建应用

app/src/main/res/layout/activity_my.xml

布局文件 Text View App bar Floating action button Material Design

app/src/main/java/com.example.myfirstapp/MyActivity.java

start activity load layout file

app/src/main/AndroidManifest.xml

fundamental characteristics of the app define components

app/build.gradle

• 使用Gradle编译和构建App
• compiledSdkVersion: 编译App的平台版本
• applicationId
• minSdkVersion
• targetSdkVersion
• Building Your Project with Gradle

/res包含应用的resources

• drawable-density: drawable resources
• layout: user interface
• menu
• mipmap: Launcher icons
• values

在真机上运行

• Enable USB debugging

通过command line运行

gradlew.bat assembleDebug
adb install app/build/outputs/apk/app-debug.apk

创建简单User Interface

• View: UI widgets such as buttions or text fields
• ViewGroup: invisible view containers
• Define UI in XML using a hierarchy of UI elements
• Layouts are subclasses of the ViewGroup

创建线性布局 Linear Layout

• 修改content_my.xml为：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:showIn="@layout/activity_my">

添加 Text Field

<EditText android:id="@+id/edit_message"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:hint="@string/edit_message" />

添加 Button

<Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_send"/>

Make the Input Box Fill in the Screen Width

android:layout_weight="1"
android:layout_width="0dp"

启动另一个Activity

• 为Button添加android:onClick属性

<Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/button_send"
        android:onClick="sendMessage" />

• 在MyActivity.java中添加sendMessage方法

public void sendMessage(View view) {
  // Do something in response to button
}

public void 参数唯一（View类型，代表被点击的视图）

创建Intent

Intent intent = new Intent(this, DisplayMessageActivity.class);
EditText editText = (EditText) findViewById(R.id.edit_message);
String message = editText.getText().toString();
intent.putExtra(EXTRA_MESSAGE, message);
startActivity(intent);

创建DisplayMessageActivity

接收Intent中的消息

Intent intent = getIntent();
String message = intent.getStringExtra(MyActivity.EXTRA_MESSAGE);