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n1ce2cv

园龄：5年2个月粉丝：4关注：1

基础控件(ListView,RecyclerView,单位和尺寸,ViewPager,ViewPager2)

ListView

  • list_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <TextView
        android:id="@+id/tv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="30sp"
        android:text="haha"/>
</LinearLayout>
  • activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <ListView
        android:id="@+id/lv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
 
</LinearLayout>
  • Bean.java
package com.example.mylistview;
 
public class Bean {
    String name;
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
}
  • MainActivity.java
package com.example.mylistview;
 
import androidx.appcompat.app.AppCompatActivity;
 
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ListView;
 
import java.util.ArrayList;
import java.util.List;
 
public class MainActivity extends AppCompatActivity {
 
    private List<Bean> data = new ArrayList<>();
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        for (int i = 0; i < 100; i++) {
            Bean bean = new Bean();
            bean.setName("haha" + i);
            data.add(bean);
        }
 
        ListView listView = findViewById(R.id.lv);
        listView.setAdapter(new MyAdapter(data, this));
        listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
            @Override
            public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
                Log.e("wmj", "onItemClick:" + i);
            }
        });
 
    }
}
  • 普通版MyAdapter.java
package com.example.mylistview;
 
import android.content.Context;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
 
import java.util.List;
 
public class MyAdapter extends BaseAdapter {
 
    private List<Bean> data;
    private Context context;
 
    public MyAdapter(List<Bean> data, Context context) {
        this.data = data;
        this.context = context;
    }
 
    @Override
    public int getCount() {
        return data.size();
    }
 
    @Override
    public Object getItem(int i) {
        return null;
    }
 
    @Override
    public long getItemId(int i) {
        return i;
    }
 
    // 每显示一个item都会调用一次
    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
        if(view == null){
            view = LayoutInflater.from(context).inflate(R.layout.list_item, viewGroup, false);
        }
        TextView textView = view.findViewById(R.id.tv);
        textView.setText(data.get(i).getName());
 
        Log.e("wmj", "getView:" + i);
 
        return view;
    }
    
}
  • 优化后的My Adapter.java，减少findviewbyid的时间
package com.example.mylistview;
 
import android.content.Context;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.BaseAdapter;
import android.widget.TextView;
 
import java.util.List;
 
public class MyAdapter extends BaseAdapter {
 
    private List<Bean> data;
    private Context context;
 
    public MyAdapter(List<Bean> data, Context context) {
        this.data = data;
        this.context = context;
    }
 
    @Override
    public int getCount() {
        return data.size();
    }
 
    @Override
    public Object getItem(int i) {
        return null;
    }
 
    @Override
    public long getItemId(int i) {
        return i;
    }
 
    // 每显示一个item都会调用一次
    @Override
    public View getView(int i, View view, ViewGroup viewGroup) {
 
        ViewHolder viewHolder;
 
        if(view == null){
            // viewHolder和view都只要创建一个就行，反复使用
            viewHolder = new ViewHolder();
            view = LayoutInflater.from(context).inflate(R.layout.list_item, viewGroup, false);
            viewHolder.textView = view.findViewById(R.id.tv);
            view.setTag(viewHolder);
        }else{
            // 如果view已存在，就从服用之前的viewHolder
            viewHolder = (ViewHolder) view.getTag();
        }
        viewHolder.textView.setText(data.get(i).getName());
 
        Log.e("wmj", "getView:" + i);
 
        return view;
    }
 
    private final class ViewHolder{
        TextView textView;
    }
}

RecyclerView

  • 在build.gradle中添加依赖：implementation 'androidx.recyclerview:recyclerview:1.1.0'
  • recyclerview_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <TextView
        android:id="@+id/tv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:textSize="30sp"
        android:text="haha"/>
</LinearLayout>
  • activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/rv"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
 
</LinearLayout>
  • Bean.java
package com.example.myrecyclerview;
 
public class Bean {
    String name;
 
    public String getName() {
        return name;
    }
 
    public void setName(String name) {
        this.name = name;
    }
}
  • MainActivity.java
package com.example.myrecyclerview;
 
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.GridLayoutManager;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import androidx.recyclerview.widget.StaggeredGridLayoutManager;
 
import android.os.Bundle;
import android.util.Log;
import android.widget.LinearLayout;
import android.widget.Toast;
 
import java.util.ArrayList;
import java.util.List;
 
public class MainActivity extends AppCompatActivity {
 
    private List<Bean> data = new ArrayList<>();
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        for (int i = 0; i < 100; i++) {
            Bean bean = new Bean();
            bean.setName("haha" + i);
            data.add(bean);
        }
 
        RecyclerView recyclerView = findViewById(R.id.rv);
 
        // 设置布局
//        LinearLayoutManager linearLayoutManager = new LinearLayoutManager(this);
//        linearLayoutManager.setOrientation(LinearLayoutManager.HORIZONTAL);
//        recyclerView.setLayoutManager(linearLayoutManager);
 
        // 参数2是指一行几个
//        GridLayoutManager gridLayoutManager = new GridLayoutManager(this, 3);
//        recyclerView.setLayoutManager(gridLayoutManager);
 
        StaggeredGridLayoutManager staggeredGridLayoutManager = new StaggeredGridLayoutManager(3, LinearLayout.VERTICAL);
        recyclerView.setLayoutManager(staggeredGridLayoutManager);
 
        MyAdapter myAdapter = new MyAdapter(data, this);
        recyclerView.setAdapter(myAdapter);
        myAdapter.setOnRecyclerItemClickListener(new MyAdapter.OnRecyclerItemClickListener() {
            @Override
            public void onRecyclerItemClick(int position) {
                Log.e("wmj", "onRecyclerItemClick:" + position);
                Toast.makeText(MainActivity.this, String.valueOf(position), Toast.LENGTH_SHORT).show();
            }
        });
 
    }
}
  • MyAdapter.java
package com.example.myrecyclerview;
 
import android.content.Context;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import android.widget.Toast;
 
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
 
import java.util.List;
 
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> {
 
    private List<Bean> data;
    private Context context;
 
    public MyAdapter(List<Bean> data, Context context) {
        this.data = data;
        this.context = context;
    }
 
    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = View.inflate(context, R.layout.recyclerview_item, null);
        return new MyViewHolder(view);
    }
 
    @Override
    public void onBindViewHolder(@NonNull MyAdapter.MyViewHolder holder, int position) {
        holder.tv.setText(data.get(position).getName());
    }
 
    @Override
    public int getItemCount() {
        return data == null ? 0 : data.size();
    }
 
    public class MyViewHolder extends RecyclerView.ViewHolder{
 
        private TextView tv;
 
        public MyViewHolder(@NonNull View itemView) {
            super(itemView);
 
            tv = itemView.findViewById(R.id.tv);
 
            itemView.setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View view) {
                    if(onRecyclerItemClickListener != null){
                        // 执行接口里的监听方法
                        onRecyclerItemClickListener.onRecyclerItemClick(getAdapterPosition());
                    }
                }
            });
        }
    }
 
    // 点击监听
    private OnRecyclerItemClickListener onRecyclerItemClickListener;
 
    // 给外部设置监听的方法
    public void setOnRecyclerItemClickListener(OnRecyclerItemClickListener onRecyclerItemClickListener) {
        this.onRecyclerItemClickListener = onRecyclerItemClickListener;
    }
 
    public interface OnRecyclerItemClickListener{
        void onRecyclerItemClick(int position);
    }
}

单位和尺寸

package com.example.mylayoutparams;
 
import androidx.appcompat.app.AppCompatActivity;
 
import android.os.Bundle;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
//        setContentView(R.layout.activity_main);
 
        LinearLayout linearLayout = new LinearLayout(this);
        LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT,
                ViewGroup.LayoutParams.MATCH_PARENT);
        linearLayout.setLayoutParams(layoutParams);
 
        TextView textView = new TextView(this);
        textView.setText("文本框");
        textView.setBackgroundColor(0xffff0000);
        // 单位默认是像素px
        ViewGroup.LayoutParams textLayoutParams = new LinearLayout.LayoutParams(300,300);
//        textView.setLayoutParams(textLayoutParams);
//        linearLayout.addView(textView);
        linearLayout.addView(textView, textLayoutParams);
 
        setContentView(linearLayout);
    }
}

ViewPager

  1. 定义一个viewpager
  2. 为viewpager构建Adapter
  • layout1.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:orientation="vertical"
    android:background="#00ff00"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="layout1"
        android:textSize="30sp"/>
 
</LinearLayout>
  • activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <androidx.viewpager.widget.ViewPager
        android:id="@+id/vp"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
</LinearLayout>
  • MainActivity.java
package com.example.myviewpager;
 
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager.widget.ViewPager;
 
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.View;
 
import java.util.ArrayList;
import java.util.List;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        LayoutInflater lf = getLayoutInflater().from(this);
        View view1 = lf.inflate(R.layout.layout1, null);
        View view2 = lf.inflate(R.layout.layout2, null);
        View view3 = lf.inflate(R.layout.layout3, null);
 
        List<View> viewList = new ArrayList<>();
        viewList.add(view1);
        viewList.add(view2);
        viewList.add(view3);
 
        ViewPager viewPager = findViewById(R.id.vp);
        MyAdapter myAdapter = new MyAdapter(viewList);
        viewPager.setAdapter(myAdapter);
    }
}
  • MyAdapter.java
package com.example.myviewpager;
 
import android.view.View;
import android.view.ViewGroup;
 
import androidx.annotation.NonNull;
import androidx.viewpager.widget.PagerAdapter;
 
import java.util.List;
 
public class MyAdapter extends PagerAdapter {
 
    List<View> mListView;
 
    public MyAdapter(List<View> mListView) {
        this.mListView = mListView;
    }
 
    @Override
    public int getCount() {
        return mListView.size();
    }
 
    // 将给定位置的view添加到viewgroup容器中，创建并显示出来
    @NonNull
    @Override
    public Object instantiateItem(@NonNull ViewGroup container, int position) {
        container.addView(mListView.get(position), 0);
        return mListView.get(position);
    }
 
    @Override
    public boolean isViewFromObject(View view,Object object) {
        return view == object;
    }
 
    @Override
    public void destroyItem(@NonNull ViewGroup container, int position, @NonNull Object object) {
        container.removeView(mListView.get(position));
    }
}

ViewPager2

  • 添加依赖：implementation 'androidx.viewpager2:viewpager2:1.0.0'
  • activity_main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <androidx.viewpager2.widget.ViewPager2
        android:id="@+id/vp"
        android:background="#ffff00"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>
 
</LinearLayout>
  • item_pager.xml
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout android:layout_height="match_parent"
    android:layout_width="match_parent"
    android:id="@+id/container"
    xmlns:android="http://schemas.android.com/apk/res/android">
 
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:id="@+id/tvTitle"
        android:text="haha"
        android:textColor="#ff0000"/>
 
</RelativeLayout>
  • MainActivity.java
package com.example.myviewpager2;
 
import androidx.appcompat.app.AppCompatActivity;
import androidx.viewpager2.widget.ViewPager2;
 
import android.os.Bundle;
 
public class MainActivity extends AppCompatActivity {
 
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
 
        ViewPager2 viewPager = findViewById(R.id.vp);
        ViewPagerAdapter viewPagerAdapter = new ViewPagerAdapter();
        viewPager.setAdapter(viewPagerAdapter);
    }
}
  • ViewPagerAdapter.java
package com.example.myviewpager2;
 
import android.graphics.drawable.Drawable;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.RelativeLayout;
import android.widget.TextView;
 
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
 
import java.util.ArrayList;
import java.util.List;
 
public class ViewPagerAdapter extends RecyclerView.Adapter<ViewPagerAdapter.ViewPagerViewHolder> {
 
    private List<String> titles = new ArrayList<>();
    private List<Integer> colors = new ArrayList<>();
 
    public ViewPagerAdapter(){
        titles.add("haha");
        titles.add("xixi");
        titles.add("hehe");
        titles.add("enen");
 
        colors.add(R.color.white);
        colors.add(R.color.purple_200);
        colors.add(R.color.purple_500);
        colors.add(R.color.purple_700);
    }
 
    // 子布局必须是march_parent，否则这个函数不会执行
    @NonNull
    @Override
    public ViewPagerViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.item_pager, parent, false)
        return new ViewPagerViewHolder(view);
    }
 
    @Override
    public void onBindViewHolder(@NonNull ViewPagerViewHolder holder, int position) {
        holder.mTv.setText(titles.get(position));
        // 填进去的是资源id
        holder.mContainer.setBackgroundResource(colors.get(position));
    }
 
    @Override
    public int getItemCount() {
        return 4;
    }
 
    class ViewPagerViewHolder extends RecyclerView.ViewHolder{
 
        private TextView mTv;
        private RelativeLayout mContainer;
 
        public ViewPagerViewHolder(@NonNull View itemView) {
            super(itemView);
            mContainer = itemView.findViewById(R.id.container);
            mTv = itemView.findViewById(R.id.tvTitle);
        }
    }
}

Menu

  • 在res中添加menu文件夹，新建menu.xml
<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:id="@+id/add_item"
        android:title="Add"/>
    <item
        android:id="@+id/remove_item"
        android:title="Remove"/>
</menu>
  • 在Activity中重写onCreateOptionsMenu()，快捷键ctrl+o
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    getMenuInflater().inflate(R.menu.menu, menu);
    // 返回true表示允许创建的菜单显示出来
    return true;
}
  • 重写onOptionsItemSelected()实现菜单按钮点击
@Override
public boolean onOptionsItemSelected(@NonNull MenuItem item) {
    switch (item.getItemId()){
        case R.id.add_item:
            Toast.makeText(this, "add", Toast.LENGTH_SHORT).show();
            break;
        case R.id.remove_item:
            Toast.makeText(this, "remove", Toast.LENGTH_SHORT).show();
            // 等同于按下Back键
            finish();
            break;
        default:
    }
    return true;
}

本文作者：n1ce2cv

本文链接：https://www.cnblogs.com/sprinining/p/14955019.html

版权声明：本作品采用知识共享署名-非商业性使用-禁止演绎 2.5 中国大陆许可协议进行许可。

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