第五、六周

本文主要是介绍第五、六周，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

1.返回键实现对话框弹出是否退出应用程序

package com.example.dfsfrr;

import android.os.Bundle;
import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.view.Menu;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity {

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

        // 获取到btn2按钮
        Button btn2 = (Button) findViewById(R.id.btn_2);// 低版本的SDK必须强制类型转换

        // 设置监听事件
        btn2.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Toast.makeText(MainActivity.this, "按钮2被点击", 0).show();// 第一个参数是上线文参数，表示要在哪里显示
            }
        });

    }

    public void click1(View v) {
        Toast.makeText(this, "按钮1被点击", 0).show();

    }

    // 当点击返回按钮时
    public void onBackPressed() {
        AlertDialog dialog;
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setIcon(R.drawable.ic_launcher);
        builder.setTitle("普通对话框");
        builder.setMessage("是否退出应用程序？");
        builder.setPositiveButton("确定", new DialogInterface.OnClickListener() {

            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.dismiss();
                MainActivity.this.finish();// 主窗口关闭

            }
        });
        builder.setNegativeButton("取消", new DialogInterface.OnClickListener() {

            @Override
            public void onClick(DialogInterface dialog, int which) {
                dialog.dismiss();

            }
        });

        dialog = builder.create();
        dialog.show();

    }

}

2.实现以下场景：从一个activity中点击一个按钮后，弹出一个单选按钮对话框，上面有“男”“女”两个选项，选定后，TOAST弹出 你选择了男，或你选择了女（参考书上改字体）

package com.example.myapplication;
 
import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;
 
import android.content.DialogInterface;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;
 
public class Demo4Activity extends AppCompatActivity implements View.OnClickListener {
 
    private String[] sexArry={"男","女"};
    private int sex=0;
    private TextView textView;
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_demo4);
 
        findViewById(R.id.bt).setOnClickListener(this);
    }
 
 
    @Override
    public void onClick(View view) {
        AlertDialog dialog;
        AlertDialog.Builder builder=new AlertDialog.Builder(this)
            .setTitle("选择你的性别")
            .setSingleChoiceItems(new String[]{"男", "女"},sex, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int i) {
                    sex=i;
                }
            })
                .setPositiveButton("确定", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int i) {
                        dialog.dismiss();
                        if (sex==0){
                            Toast.makeText(Demo4Activity.this, "你选择的性别是男", Toast.LENGTH_SHORT).show();
                        }else{
                            Toast.makeText(Demo4Activity.this, "你选择的性别是女", Toast.LENGTH_SHORT).show();
                        }
 
                    }
                })
                .setNegativeButton("取消", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int i) {
                        dialog.dismiss();
                    }
                });
 
        dialog=builder.create();
        dialog.show();
 
    }
}

<?xml version="1.0" encoding="utf-8"?>
<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"
    tools:context=".Demo4Activity"
    android:orientation="vertical">

    <Button
        android:id="@+id/bt"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="按钮"
        android:textSize="50dp"
        android:layout_gravity="center"
        android:layout_marginTop="100dp"
        />


</LinearLayout>

3.布局(详见:Android第五周上机word文档)

<?xml version="1.0" encoding="utf-8"?>
<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"
    tools:context=".Demo5Activity"
    android:orientation="vertical"
    android:background="#18DF00">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="1.TextView显示文本信息"
        android:textColor="#FD0101"
        android:textSize="25dp"
        android:layout_gravity="center"
        android:layout_marginTop="20dp"
        android:textStyle="italic"/>
    <Button
        android:layout_width="350dp"
        android:layout_height="wrap_content"
        android:text="2.按钮"
        android:textColor="#FF0000"
        android:layout_gravity="center"/>
    <EditText
        android:layout_width="350dp"
        android:layout_height="wrap_content"
        android:hint="3.编辑框：请输入信息"
        android:textColorHint="#F80101"
        android:layout_gravity="center"/>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="horizontal">
        <RadioButton
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="4.男"
            android:textColor="#FF0000"
            android:layout_marginLeft="25dp"/>
        <RadioButton
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="5.女"
            android:textColor="#FF0000"/>

    </LinearLayout>
    <CheckBox
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="电脑"
        android:textColor="#FF0000"
        android:layout_marginLeft="25dp"/>
    <CheckBox
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="手机"
        android:textColor="#FF0000"
        android:layout_marginLeft="25dp"/>



</LinearLayout>

4.教材p76页 图3—17购物商城界面

package com.example.myapplication;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.ListView;
import android.widget.TextView;

public class Demo6Activity extends AppCompatActivity {

    private ListView mListView;
    private String[] titles={"桌子","苹果","蛋糕","线衣","猕猴桃","围巾"};
    private String[] prices={"1800元","10元/kg","300元","350元","10元/kg","280元"};
    private int[] icons={R.drawable.table,R.drawable.apple,R.drawable.cake,R.drawable.wireclothes,R.drawable.kiwifruit,R.drawable.scarf};
    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_demo6);
        mListView=(ListView) findViewById(R.id.lv);
        MyBaseAdapter mAdapter=new MyBaseAdapter();
        mListView.setAdapter(mAdapter);

    }
    class MyBaseAdapter extends BaseAdapter{
        public int getCount(){
            return titles.length;
        }
        public Object getItem(int position){
            return titles[position];

        }
        public long getItemId(int position){
            return position;
        }
        public View getView(int position, View convertView, ViewGroup parent){
            View view=View.inflate(Demo6Activity.this,R.layout.list_item,null);
            TextView title=view.findViewById(R.id.title);
            TextView price=view.findViewById(R.id.price);
            ImageView iv=view.findViewById(R.id.iv);
            title.setText(titles[position]);
            price.setText(prices[position]);
            iv.setBackgroundResource(icons[position]);
            return view;
        }
    }
}

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp">
    <ImageView
        android:id="@+id/iv"
        android:layout_width="120dp"
        android:layout_height="90dp"
        android:layout_centerVertical="true"/>
    <RelativeLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginLeft="10dp"
        android:layout_toRightOf="@id/iv"
        android:layout_centerVertical="true">
        <TextView
            android:id="@+id/title"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="桌子"
            android:textSize="20sp"
            android:textColor="#000000"/>
        <TextView
            android:id="@+id/tv_price"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="价格"
            android:textSize="20sp"
            android:textColor="#FF8F03"
            android:layout_marginTop="10dp"
            android:layout_below="@id/title"/>
        <TextView
            android:id="@+id/price"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="1000"
            android:textSize="20sp"
            android:textColor="#38EE74"
            android:layout_below="@id/title"
            android:layout_toRightOf="@id/tv_price"
            android:layout_marginTop="10dp"/>
    </RelativeLayout>

</RelativeLayout>

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".Demo6Activity"
    android:orientation="vertical">
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="45dp"
        android:text="购物商城"
        android:textSize="18sp"
        android:textColor="#FFFFFF"
        android:background="#FF8F03"
        android:gravity="center"/>
    <ListView
        android:id="@+id/lv"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"/>

</LinearLayout>

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