目录

• 1、启动新Activty
• 1.1、功能分析
• 1.2、开发视图布局
• 1.3、按钮事件响应
• 1.4、测试结果
• 2、启动其他App
• 2.1、功能分析
• 2.2、开发视图布局
• 2.3、按钮事件响应
• 2.4、测试结果
• 总结

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    tools:context=".CreateMessageActivity">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <EditText
            android:id="@+id/input"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:ems="10"
            android:hint="@string/hint"
            android:inputType="textPersonName"
            android:textSize="30sp"/>

        <Button
            android:id="@+id/button"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:onClick="onSendMessage"
            android:text="@string/send"
            android:textSize="30sp"
            />

    </LinearLayout>
</androidx.constraintlayout.widget.ConstraintLayout>

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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"
    app:layout_constraintRight_toRightOf="parent"
    tools:context=".ReceiveMessageActivity">

    <TextView
        android:id="@+id/output"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="2nd Activity"
        android:textSize="34sp"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent" />
</androidx.constr

<resources>
    <string name="app_name">Messager</string>
    <string name="send">Send Message</string>
    <string name="hint">Enter a message</string>
    <string name="choser">Send Message via ...</string>
</resources>

public class CreateMessageActivity extends AppCompatActivity {

    //定义常量，作为消息的key
    public static final String MESSAGE_KEY="szst.it.ping.messager";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_create_message);
    }

    public void onSendMessage(View Button){
        //获得编辑框引用
        EditText editText = findViewById(R.id.input);
        //取出编辑框文字
        String message = editText.getText().toString();

        //Intent是Android中的信使，新建Intent打开，设置收件Activity为ReceiveMessageActivity
        Intent intent = new Intent(this,ReceiveMessageActivity.class) ;
        //在intent中附加消息
        intent.putExtra(MESSAGE_KEY,message);
        //向Android发出请求
        startActivity(intent);

    }
}

public class ReceiveMessageActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_receive_message);

        //获得intent的引用
        Intent intent = getIntent();

        //根据key取出value
        String message = intent.getStringExtra(CreateMessageActivity.MESSAGE_KEY);

        //获得文本框内容，设置文字
        TextView textView = findViewById(R.id.output);
        textView.setText(message);
    }
}

public class CreateMessageActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_create_message);
    }

    public void onSendMessage(View Button){
        //获得编辑框引用
        EditText editText = findViewById(R.id.input);
        //取出编辑框文字
        String message = editText.getText().toString();

        //使用new Intent(Intent.ACTION_SEND)替换new Intent(this, ReceiveMessageActivity.class)，不知道其它App中的类名
        Intent intent = new Intent(Intent.ACTION_SEND);
        //设置消息类型为纯文本，系统不会对消息进行处理
        intent.setType("text/plain");
        //向Intent添加附加信息
        intent.putExtra(Intent.EXTRA_TEXT,message);

        //自定义选择对话框
        String chooserTitle = getString(R.string.choser);
        Intent chosenIntent = Intent.createChooser(intent, chooserTitle);

        startActivity(chosenIntent) ;
    }
}

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目录

• 一.组合widget实现
• 二.通过自定义CustomPainter实现widgets
• 三.饼状图piechart.dart代码展示
• 四.实际效果图,eg:
• 附：Flutter中父widget调用子widget的方法
• 总结

import ''package:flutter/material.dart'';
 
class CustomButtonTest extends StatelessWidget{
  final String textStr;
  CustomButtonTest(this.textStr);
 
  @override
  Widget build(BuildContext context) {
    return RaisedButton(
      onPressed: (){},
      child: Text(
        textStr,
        textAlign: TextAlign.center,
      )
    );
  }
 
}

@override
  Widget build(BuildContext context) {
    return new Center(
      child: new CustomButton("Custom Button"),
    );
  }
}

Paint _paint = new Paint()
..color = Colors.red // 画笔颜色 
..strokeCap = StrokeCap.round //画笔笔触类型,包括(1.round-画笔笔触呈半圆形轮廓开始和结束;2.butt-笔触开始和结束边缘平坦，没有外延;3.square-笔触开始和结束边缘平坦,向外延伸长度为画笔宽度的一半)
..isAntiAlias = true //是否启动抗锯齿
..style=PaintingStyle.fill //绘画风格，默认为填充，有fill和stroke两种
..blendMode=BlendMode.exclusion //颜色混合模式
..colorFilter=ColorFilter.mode(Colors.blueAccent, BlendMode.exclusion)//颜色渲染模式
..maskFilter=MaskFilter.blur(BlurStyle.inner, 3.0)//模糊遮罩效果
..filterQuality=FilterQuality.high//颜色渲染模式的质量
..strokeWidth = 15.0;//画笔的宽度复制代码

void drawRect(Rect rect, Paint paint) {...} //画矩形
void drawLine(Offset p1, Offset p2, Paint paint) {...} //画线
void drawPoints(PointMode pointMode, List<Offset> points, Paint paint) {...} //画点
void drawCircle(Offset c, double radius, Paint paint) {...} //画圆
void drawArc(Rect rect, double startAngle, double sweepAngle, bool useCenter, Paint paint) {...} //画圆弧

import ''dart:math'';
import ''package:flutter/material.dart'';
 
class PieChartTest extends StatelessWidget{
  const PieChartTest({Key? key}) : super(key: key);
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text(''pie chart''),
      ),
      body:Container(
        alignment: Alignment.center,
        child: CustomPaint(
          size: const Size(300, 300),
          painter: PieChartPainter(),
        ),
      )
    );
  }
}
 
class PieChartPainter extends CustomPainter{
 
  Paint getColoredPaint(Color color){
    Paint paint=Paint();
    paint.color=color;
    return paint;
  }
 
  @override
  void paint(Canvas canvas, Size size) {
    double wheelSize=min(size.width, size.height)/2;
    double nbElem=8;
    double radius=(2*pi)/nbElem;
    Rect boundingRect=Rect.fromCircle(center: Offset(wheelSize,wheelSize), radius: wheelSize);
    canvas.drawArc(boundingRect, 0, radius, true, getColoredPaint(Colors.orange));
    canvas.drawArc(boundingRect, radius, radius, true, getColoredPaint(Colors.black));
    canvas.drawArc(boundingRect, radius*2, radius, true, getColoredPaint(Colors.green));
    canvas.drawArc(boundingRect, radius*3, radius, true, getColoredPaint(Colors.red));
    canvas.drawArc(boundingRect, radius*4, radius, true, getColoredPaint(Colors.blue));
    canvas.drawArc(boundingRect, radius*5, radius, true, getColoredPaint(Colors.yellow));
    canvas.drawArc(boundingRect, radius*6, radius, true, getColoredPaint(Colors.purple));
    canvas.drawArc(boundingRect, radius*7, radius, true, getColoredPaint(Colors.white));
  }
 
  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate)=>oldDelegate!=this;
}

final _childWidgetKey = GlobalKey();

ChildPage(key:_receiveKey),

class ChildPage extends StatefulWidget {undefined
ChildPage({Key key}) : super(key: key);
​​​​​​​@override
ChildPageState createState() => ChildPageState();
}

_childWidgetKey.currentState.onRefresh();

• Flutter Widgets粘合剂CustomScrollView NestedScrollView滚动控件
• Flutter Widgets之标签类控件Chip详解
• Flutter开发Widgets 之 PageView使用示例
• Flutter Widgets MediaQuery控件屏幕信息适配

export GOROOT=/usr/local/go
export GOPATH=$HOME/go
export PATH=$PATH:$GOROOT/bin:$GOPATH/bin