欢迎您访问程序员文章站本站旨在为大家提供分享程序员计算机编程知识!
您现在的位置是: 首页  >  移动技术

安卓开发入门,基础语法介绍

程序员文章站 2022-06-24 18:45:55
安卓b站学习笔记梳理2020.11.27天哥在奔跑安卓教程b站网址https://www.bilibili.com/video/BV1Rt411e769.ImageView①Button的其他衍生控件:ToggleButton、Switch②常用属性③加载网络图片...

安卓b站学习笔记梳理2020.11.27

天哥在奔跑安卓教程b站网址https://www.bilibili.com/video/BV1Rt411e76

目录

安卓b站学习笔记梳理2020.11.27

9.ImageView

①Button的其他衍生控件:ToggleButton、Switch

②常用属性

③加载网络图片 

10.列表视图ListView(快被淘汰了)

①ListViewActivity.java

②常用属性(activity_listview.xml文件里的)

③Adapter接口(跟ListViewActivity同在listView文件夹下的MyListAdapter.java文件内容如下)

④R.layout.layout_list_item(每个item的内容布局,在MyListAdapter.java中convertView有使用)

⑤list_item.xml(在activity_listview.xml中的中用drawable)


9.ImageView

①Button的其他衍生控件:ToggleButton、Switch

自行百度

②常用属性

<ImageView
    android:id="@+id/iv_1"
    android:layout_width="200dp"
    android:layout_height="120dp"
    android:background="#FF9900"
    android:src="@drawable/png1"
    android:scaleType="fitXY"
/>

注意scaleType:

  1. fitXY:撑满控件,宽高比可能发生变化
  2. fitCenter:保持宽高比缩放,直至能够完全显示
  3. centerCrop:保持宽高比缩放,直至完全覆盖控件,裁剪显示

③加载网络图片 

  1. 使用第三方glide库https://github.com/bumptech/glide(里面有各种文档)

     use Gradle:

    repositories {
      google()
      jcenter()
    }
    
    dependencies {
      implementation 'com.github.bumptech.glide:glide:4.11.0'
      annotationProcessor 'com.github.bumptech.glide:compiler:4.11.0'
    }

    需要做的事情:在build.gradle文件中加入上面repositories的代码,并且在dependencies下面加入上面denpendencied的两行代码

  2. 在AndroidManifest.xml文件中加入以下代码表示可连接网络的权限
    <uses-permission android:name="android.permission.INTERNET"/>
  3. ImageViewActivity.java中引用代码如下(前提是xml里面先有一个ImageView)
public class ImageViewActivity extends AppCompatActivity {
    private ImageView mIv3;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_image_view);
        mIv3 = findViewById(R.id.iv_3);

        Glide.with(this).load("https://tb2.bdstatic.com/tb/static-common/img/search_logo_big_v1_8d039f9.png").into(mIv3);
    }
}

10.列表视图ListView(快被淘汰了)

①ListViewActivity.java

package com.jz.application1.listView;
import android.app.Activity;
import android.os.Bundle;
import android.widget.ListView;
import androidx.annotation.Nullable;
import com.jz.application1.R;

public class ListViewActivity extends Activity {

    private ListView mLv1;

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

        mLv1 = findViewById(R.id.lv_1);
        mLv1.setAdapter(new MyListAdapter(ListViewActivity.this));

    }
}

②常用属性(activity_listview.xml文件里的)

<ListView
    android:id="@+id/lv_1"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:listSelector="@drawable/list_item"/>

③Adapter接口(跟ListViewActivity同在listView文件夹下的MyListAdapter.java文件内容如下)

package com.jz.application1.listView;

import android.annotation.SuppressLint;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import com.bumptech.glide.Glide;
import com.jz.application1.R;


public class MyListAdapter extends BaseAdapter{
    private Context mContext;
    private LayoutInflater mLayoutInflater;

    public MyListAdapter(Context context){
        this.mContext = context;
        mLayoutInflater = LayoutInflater.from(context);
    }

    @Override
    public int getCount() {
        return 10;
    }

    @Override
    public Object getItem(int position) {
        return null;
    }

    @Override
    public long getItemId(int position) {
        return 0;
    }

    static class ViewHolder{
        public ImageView imageView;
        public TextView tvTitle,tvTime,tvContent;
    }

    @SuppressLint({"SetTextI18n", "InflateParams"})//根据警报加的
    @Override
    public View getView(int position, View convertView, ViewGroup parent) {

        ViewHolder holder = null;

        if(convertView == null){
            convertView = mLayoutInflater.inflate(R.layout.layout_list_item,null);
            holder = new ViewHolder();
            holder.imageView = convertView.findViewById(R.id.iv);
            holder.tvTitle = convertView.findViewById(R.id.tv_title1);
            holder.tvTime = convertView.findViewById(R.id.tv_time);
            holder.tvContent = convertView.findViewById(R.id.tv_content);
            convertView.setTag(holder);
        }else {
            holder = (ViewHolder) convertView.getTag();
        }

        //apply values to controller
        holder.tvTitle.setText("This is title");
        holder.tvTime.setText("2088-08-08");
        holder.tvContent.setText("This is content!");
        Glide.with(mContext).load("https://tb2.bdstatic.com/tb/static-common/img/search_logo_big_v1_8d039f9.png").into(holder.imageView);
        return convertView;
    }
}

④R.layout.layout_list_item(每个item的内容布局,在MyListAdapter.java中convertView有使用)

使用方式:

convertView = mLayoutInflater.inflate(R.layout.layout_list_item,null);
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="horizontal"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingLeft="15dp"
    android:paddingRight="15dp"
    android:paddingTop="10dp"
    android:paddingBottom="10dp">

    <ImageView
        android:id="@+id/iv"
        android:layout_width="100dp"
        android:layout_height="100dp"
        android:scaleType="fitCenter"
        android:background="#000000"
        />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical"
        android:paddingLeft="10dp">
        <TextView
            android:id="@+id/tv_title1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="hello"
            android:textSize="20sp"
            android:textColor="@color/colorBlack"/>
        <TextView
            android:id="@+id/tv_time"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:textSize="28sp"
            android:text="2020-11-27"
            android:textColor="@color/colorGrayDark"/>
        <TextView
            android:id="@+id/tv_content"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="10dp"
            android:textColor="@color/colorGrayDark"
            android:textSize="18sp"
            android:text="This is content"/>
    </LinearLayout>
</LinearLayout>

⑤list_item.xml(在activity_listview.xml中的<ListView>中用drawable)

使用方式:

android:listSelector="@drawable/list_item"

实现效果:点击会有颜色变化

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_selected="true"
        android:drawable="@color/colorOrange"/>
    <item android:state_pressed="true"
        android:drawable="@color/colorGrayDark"/>
    <item android:state_focused="true"
        android:drawable="@color/colorAccent"/>
    <item
        android:drawable="@color/colorPrimary"/>
</selector>

 

 

本文地址:https://blog.csdn.net/weixin_42898615/article/details/110239497