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
- 定义一个viewpager
- 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;
}
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