android 每行显示3个 android第三行代码

《第一行代码》第三章

目录

• 《第一行代码》第三章

• 控件篇

• TextView
• Button
• TextView
• ImageView
• ProgressDialog
• ListView
• 定制ListView
• 更强大的滚动控件——RecyclerView

• 横向
• 瀑布流

• 布局篇

• 线性布局——LinearLayout
• 相对布局——RelativeLayout
• 帧布局——FrameLayout
• 百分比布局

• 自定义

• 自定义布局

界面编写实践——聊天界面在下一篇

控件篇

TextView

• 简单介绍了TextView的几个属性，其余可查阅文档即可

<TextView
        android:id="@+id/text_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
    android:gravity="center"	
    android:textSize="24sp"
    android:textColor="#00ff00"
        android:text="Hello World!" />

• "match_parent" 为适应父布局, "wrap_content" 为刚好包住文字，即文字大小
• android:gravity="center" 设置文本位置; android:textSize="24sp" 设置文字大小，以sp为单位; android:textColor="#00ff00" 设置颜色。

Button

• 略

TextView

<EditText
       android:id="@+id/edit_text"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       android:hint="Type something here"
       android:maxLines="2"
       android:text="Name" />

• android:hint="Type something here" 为提示信息;android:maxLines="2" 为最大行数。

ImageView

<ImageView
    android:id="@+id/image_view"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:src="@drawable/img_1"/>

• 修改主活动代码，完成以下效果： 展开查看

private EditText editText;
    private ImageView imageView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = (Button) findViewById(R.id.button);
        button.setOnClickListener(this);
        imageView = (ImageView) findViewById(R.id.image_view);
        editText = (EditText) findViewById(R.id.edit_text);
}@Override
public void onClick(View view) {
    switch (view.getId()) {
        case R.id.button:
            imageView.setImageResource(R.drawable.img_2);
            break;
        default:
            break;
    }
}

<ProgressBar
       android:id="@+id/progress_bar"
       android:layout_width="match_parent"
       android:layout_height="wrap_content"
       style="?android:attr/progressBarStyleHorizontal"	//设置样式，指定水平进度条，可省
     android:max="100"	//给进度条设置最大值
       />

• 所有的Android 控件都可以通过android：visibility 进行指定，可选值有三种：visible、invisible 、gone。gone 表示控件不仅不可见，而且不在占用任何屏幕空间。
• 使用 setVisibility()方法可以传入 View.VISIBLE、View.INVISIBLE、View.GONE 来控制可见性。
• 修改主活动case，完成以下效果： 展开查看

case R.id.button:
                int progress = progressBar.getProgress();
                progress = progress + 10;
                progressBar.setProgress(progress);
                break;

• 通过AlerDialog.Builder 创建一个AlertDialog 的实例，然后可以为这个对话框设置标题、内容、可否取消等属性。
• 修改case：

case R.id.button:
    AlertDialog.Builder dialog = new AlertDialog.Builder(MainActivity.this);
    dialog.setTitle("This is Dialog");
    dialog.setMessage("Something important.");
    dialog.setCancelable(false);
    dialog.setPositiveButton("OK",new DialogInterface.OnClickListener(){	//设置确定按钮
        @Override
        public void onClick(DialogInterface dialogInterface, int i) {
        }
    });
    dialog.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {	//设置取消按钮
        @Override
        public void onClick(DialogInterface dialogInterface, int i) {
        }
    });
    dialog.show();
    break;

ProgressDialog

• 修改case：

case R.id.button:
    ProgressDialog progressDialog = new ProgressDialog(MainActivity.this);
    progressDialog.setTitle("This is a ProgressDialog");
    progressDialog.setCancelable(true);	//设为true即返回就取消
    progressDialog.show();
    break;

ListView

• 主活动： 展开查看

public class MainActivity extends AppCompatActivity {
    private String[] data = {
            "Apple","aa","bb","cc","dd","ee","ff","gg","aa","bb","cc","aa","bb","cc","aa","bb","cc"
    };
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ArrayAdapter adapter = new ArrayAdapter(
            MainActivity.this, android.R.layout.simple_list_item_1, data);
    ListView listView = (ListView) findViewById(R.id.list_view);
    listView.setAdapter(adapter);
}
}

定制ListView

• 写Fruit类 展开查看

package com.example.ullayouttest;
public class Fruit {
    private String name;
    private  int imageId;
    public Fruit(String name,int imageId){
        this.name = name;
        this.imageId = imageId;
    }
    public String getName(){
        return name;
    }
    public int getImageId(){
        return imageId;
    }
}

• 重写适配器

public class FruitAdapter extends ArrayAdapter<Fruit> {
    private int resourceId;
    public FruitAdapter(Context context, int textViewResourceId, List<Fruit> objects){
        super(context,textViewResourceId,objects);
        resourceId = textViewResourceId;
    }
    public View getView(int position, View convertView, ViewGroup parent){
        Fruit fruit = getItem(position);
        View view = LayoutInflater.from(getContext()).inflate(resourceId,parent,false);
       //以下布局里传入图片与名字
        ImageView fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
        TextView fruitName = (TextView) view.findViewById(R.id.fruit_name);
        fruitImage.setImageResource(fruit.getImageId());
        fruitName.setText(fruit.getName());
        return view;
    }
}

• 修改主活动：

public class MainActivity extends AppCompatActivity {
    private List<Fruit> fruitList = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //主要
        initFruits();
        FruitAdapter adapter = new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);
        ListView listView = (ListView) findViewById(R.id.list_view);
        listView.setAdapter(adapter);
        //放进ListView
    }
    private void initFruits(){
        for (int i=0;i<2;i++){
            Fruit 南瓜 = new Fruit("南瓜",R.drawable.nangua);
            fruitList.add(南瓜);
            Fruit 土豆 = new Fruit("土豆",R.drawable.tudou);
            fruitList.add(土豆);
            Fruit 芒果 = new Fruit("芒果",R.drawable.mangguo);
            fruitList.add(芒果);
            Fruit 菠萝 = new Fruit("菠萝",R.drawable.boluo);
            fruitList.add(菠萝);
            Fruit 蘑菇 = new Fruit("蘑菇",R.drawable.mogu);
            fruitList.add(蘑菇);
            Fruit 西瓜 = new Fruit("西瓜",R.drawable.xigua);
            fruitList.add(西瓜);
            Fruit 饮料 = new Fruit("饮料",R.drawable.yinliao);
            fruitList.add(饮料);
        }
    }
}

• 布局fruit_item：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="wrap_content">
    <ImageView
        android:id="@+id/fruit_image"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"/>
    <TextView
        android:id="@+id/fruit_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical"
        android:layout_marginLeft="10dp"/>

</LinearLayout>

• 主布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
   />
    <ListView
        android:id="@+id/list_view"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>

---

• 修改主活动，优化并加入点击事件（程序不久后自动退出了？？）

public class MainActivity extends AppCompatActivity {
    private List<Fruit> fruitList = new ArrayList<>();


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //主要
        initFruits();
        FruitAdapter adapter = new FruitAdapter(MainActivity.this,R.layout.fruit_item,fruitList);
        ListView listView = (ListView) findViewById(R.id.list_view);
        listView.setAdapter(adapter);
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> parent, View view, int position, long id) {
                Fruit fruit = fruitList.get(position);
                Toast.makeText(MainActivity.this,fruit.getName(),
                        Toast.LENGTH_SHORT).show();

            }
        });
    }

更强大的滚动控件——RecyclerView

• 修改主活动中onCreate

public class MainActivity extends AppCompatActivity {
    private List<Fruit> fruitList = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //主要
        initFruits();
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rc_list);
        LinearLayoutManager layoutManager = new LinearLayoutManager(this);
       recyclerView.setLayoutManager(layoutManager);
        FruitAdapter adapter = new FruitAdapter(fruitList);
        recyclerView.setAdapter(adapter);

    }

• 修改FruitAdapter: 展开

package com.example.ullayouttest;
import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ArrayAdapter;
import android.widget.ImageView;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.List;
public class FruitAdapter extends RecyclerView.Adapter {
    private List mFruitList;
    static class ViewHolder extends RecyclerView.ViewHolder{
        ImageView fruitImage;
        TextView fruitName;
        public ViewHolder(View view){
            super(view);
            fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
            fruitName = (TextView)view.findViewById(R.id.fruit_name);
        }
    }
    public FruitAdapter(List fruitList){
        mFruitList = fruitList;
    }
    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext())          .inflate(R.layout.fruit_item,parent,false);
        ViewHolder holder = new ViewHolder(view);
        return holder;
    }
    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        Fruit fruit = mFruitList.get(position); holder.fruitImage.setImageResource(fruit.getImageId());
        holder.fruitName.setText(fruit.getName());
    }
    @Override
    public int getItemCount() {
        return mFruitList.size();
    }
}

• 主布局(书里的是android.support.xxx)：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">
/>
    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/rc_list"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
</LinearLayout>

横向

• 修改fruit_item 布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" 
    android:layout_width="100dp"
    android:layout_height="wrap_content">
    <ImageView
        android:id="@+id/fruit_image"
        android:layout_width="70dp"
        android:layout_height="70dp"
        android:layout_gravity="center_horizontal"
        />
    <TextView
        android:id="@+id/fruit_name"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_marginLeft="10dp"/>

</LinearLayout>

• 在主活动OnCreate中添加 layoutManager.setOrientation(LinearLayoutManager.HORIZONTAL); 语句

瀑布流

• 修改主活动，修改的主要代码只有一句，即 StaggeredGridLayoutManager layoutManager 修改成瀑布流。 展开

public class MainActivity extends AppCompatActivity {
    private List fruitList = new ArrayList<>();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initFruits();
        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rc_list);
        StaggeredGridLayoutManager layoutManager = new StaggeredGridLayoutManager(3,StaggeredGridLayoutManager.VERTICAL);
       recyclerView.setLayoutManager(layoutManager);
        FruitAdapter adapter = new FruitAdapter(fruitList);
        recyclerView.setAdapter(adapter);
    }
    private void initFruits(){
        for (int i=0;i<2;i++){
            Fruit 南瓜 = new Fruit( getRandomLengthName("南瓜"),R.drawable.nangua);
            fruitList.add(南瓜);
            Fruit 土豆 = new Fruit(getRandomLengthName("土豆"),R.drawable.tudou);
            fruitList.add(土豆);
            Fruit 芒果 = new Fruit(getRandomLengthName("芒果"),R.drawable.mangguo);
            fruitList.add(芒果);
            Fruit 菠萝 = new Fruit(getRandomLengthName("菠萝"),R.drawable.boluo);
            fruitList.add(菠萝);
            Fruit 蘑菇 = new Fruit(getRandomLengthName("蘑菇"),R.drawable.mogu);
            fruitList.add(蘑菇);
            Fruit 西瓜 = new Fruit(getRandomLengthName("西瓜"),R.drawable.xigua);
            fruitList.add(西瓜);
            Fruit 饮料 = new Fruit(getRandomLengthName("饮料"),R.drawable.yinliao);
            fruitList.add(饮料);
        }
    }
    private String getRandomLengthName(String name){
        Random random = new Random();
        int length = random.nextInt(20) + 1;
        StringBuilder builder = new StringBuilder();
        for(int i = 0;i<length;i++){ builder.append(name);
        }
        return= builder.tostring();
    }
}

• 
  

• 

• 瀑布流添加事件：与ListView有所不同，需要给子项具体的View添加点击事件 展开

public class FruitAdapter extends RecyclerView.Adapter {
    private List mFruitList;
    static class ViewHolder extends RecyclerView.ViewHolder{
        View fruitView;
        ImageView fruitImage;
        TextView fruitName;
        public ViewHolder(View view){
            super(view);
            fruitView = view;
            fruitImage = (ImageView) view.findViewById(R.id.fruit_image);
            fruitName = (TextView)view.findViewById(R.id.fruit_name);
        }
    }
    public FruitAdapter(List fruitList){
        mFruitList = fruitList;
    }
    @NonNull
    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext())
               .inflate(R.layout.fruit_item,parent,false);
        final ViewHolder holder = new ViewHolder(view);
        holder.fruitView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int position = holder.getAdapterPosition();
                Fruit fruit = mFruitList.get(position);
                Toast.makeText(view.getContext(),"you clicked view"+fruit.getName(),Toast.LENGTH_SHORT).show();
            }
        });
        holder.fruitImage.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                int position = holder.getAdapterPosition();
                Fruit fruit = mFruitList.get(position);
                Toast.makeText(view.getContext(),"you clicked image"+fruit.getName(),Toast.LENGTH_SHORT).show();
            }
        });
        return holder;
    }
    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        Fruit fruit = mFruitList.get(position);
        holder.fruitImage.setImageResource(fruit.getImageId());
        holder.fruitName.setText(fruit.getName());
    }
    @Override
    public int getItemCount() {
        return mFruitList.size();
    }
}

布局篇

线性布局——LinearLayout

• 通过 android:orientation="vertical" 可改变为水平排列布局。
• android:layout_gravity 用于指定控件在布局中的对齐方式。
• android:layout_weight 可使用比例的方式来指定控件的大小。

相对布局——RelativeLayout

<!--相对父布局进行对齐-->
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_alignParentBottom="true"
android:layout_alignParentRight="true"
android:layout_centerInParent="true"

<!--相对控件进行对齐-->
android:layout_above="@id/button3"
android:layout_toLeftOf="@id/button3"
android:layout_below="@id/button3"
android:layout_toRightOf="@id/button3"

        

帧布局——FrameLayout

• 所有的控件都默认摆放在布局的左上角

百分比布局

• 百分比布局————android.support.percent.PercentFrameLayout

layout_widthPercent="50%"
layout_heightPercent="50%"

---

自定义

自定义布局

• 当要添加标题栏，主活动中：

ActionBar actionBar = getSupportActionBar();
if(actionBar != null){
    actionBar.hide();
    
}

• 主活动布局添加：

<include layout="@layout/title"/>

• 布局：

android:background="@drawable/title"

自定义控件

1. 添加新的布局

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@drawable/title">
    <Button
        android:id="@+id/back"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_margin="5dp"
        android:background="@drawable/back"
        android:text="Back"
        android:textColor="#fff"/>
    <TextView
        android:id="@+id/text"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_gravity="center"
        android:layout_weight="1"
        android:gravity="center"
        android:text="Title Text"
        android:textColor="#fff"
        android:textSize="24sp"/>
    <Button
        android:id="@+id/edit"
        android:layout_width="wrap_content"
        android:layout_height="fill_parent"
        android:layout_gravity="center"
        android:layout_margin="5dp"
        android:background="@drawable/edit"
        android:text="Edit"
        android:textColor="#fff"/>
</LinearLayout>

1. 新建活动并写好相应的功能 展开查看

package com.example.ullayouttest;
import android.app.Activity;
import android.content.Context;
import android.util.AttributeSet;
import android.view.LayoutInflater;
import android.view.View;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.Toast;
public class TitleLayout extends LinearLayout {
    public TitleLayout(Context context, AttributeSet attrs){
        super(context,attrs);
        LayoutInflater.from(context).inflate(R.layout.title,this);
        Button titleBack = (Button) findViewById(R.id.back);
        Button titleEdit = (Button) findViewById(R.id.edit);
        titleBack.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View view) {
                ((Activity)getContext()).finish();
            }
        });
        titleEdit.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View view) {
                Toast.makeText(getContext(), "you clicked edit button", Toast.LENGTH_SHORT).show();
            }
        });
    }
}

1. 接下来当作普通控件使用即可

<com.example.ullayouttest.TitleLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"/>