本文详细介绍JetPack Room数据库的集成与使用，结合RecyclerView展示数据，包括普通与卡片视图切换，点击反馈及在线搜索功能。
初步了解JetPack中的Room（3）
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初步了解JetPack中的Room(3)
关于使用RecyclerView
点击下载并添加依赖，系统会自己进行添加，我们等待加载完成即可。
手动添加如下，在gradle中添加依赖：
dependencies {
implementation "androidx.recyclerview:recyclerview:1.1.0"
// For control over item selection of both touch and mouse driven selection
implementation "androidx.recyclerview:recyclerview-selection:1.1.0-rc01"
}
修改界面
RecyclerView的使用
- 将之前的TextView删除，变更为RecyclerView代码如下：
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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=".MainActivity">
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="horizontal"
app:layout_constraintGuide_percent="0.7" />
<androidx.recyclerview.widget.RecyclerView
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintBottom_toTopOf="@+id/guideline"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent" />
<Button
android:id="@+id/buttonInsert"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="insert"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/buttonUpdate"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="@+id/guideline"
app:layout_constraintVertical_bias="0.25" />
<Button
android:id="@+id/buttonUpdate"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="update"
app:layout_constraintBottom_toBottomOf="@+id/buttonInsert"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/buttonInsert"
app:layout_constraintTop_toTopOf="@+id/buttonInsert" />
<Button
android:id="@+id/buttonClear"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="clear"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/buttonDelete"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toBottomOf="@+id/buttonInsert" />
<Button
android:id="@+id/buttonDelete"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="delete"
app:layout_constraintBottom_toBottomOf="@+id/buttonClear"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.5"
app:layout_constraintStart_toEndOf="@+id/buttonClear"
app:layout_constraintTop_toTopOf="@+id/buttonClear" />
</androidx.constraintlayout.widget.ConstraintLayout>
- 创建单元布局cell_normal.layout
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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="wrap_content">
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_percent="0.1" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_percent="0.85" />
<TextView
android:id="@+id/textView"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/guideline2"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:text="1" />
<TextView
android:id="@+id/textView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:text="TextView"
android:textSize="24sp"
app:layout_constraintBottom_toTopOf="@+id/textView3"
app:layout_constraintEnd_toStartOf="@+id/guideline3"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="@+id/guideline2"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/textView3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="@+id/textView2"
app:layout_constraintTop_toBottomOf="@+id/textView2" />
</androidx.constraintlayout.widget.ConstraintLayout>
- 制作关于RecyclerView的适配器Adapter
创建一个MyAdapter类继承RecyclerView.Adapter
编写内部类MyViewHolder并添加constructor方法：
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.ArrayList;
import java.util.List;
public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder> { //<>中表示使用的ViewHolder为自己写的静态内部类MyViewHolder
List<Word> allWords = new ArrayList<>(); //初始化一个空列表
public void setAllWords(List<Word> allWords) {
this.allWords = allWords;
}
@NonNull
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
/*
* 当创建ViewHolder时
* 从Layout文件中
* 加载View
* */
LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
View itemView = layoutInflater.inflate(R.layout.cell_normal,parent,false);
return new MyViewHolder(itemView);
}
@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {
//绑定逻辑上的关联
Word word = allWords.get(position);
holder.textViewNumber.setText(String.valueOf(position));
holder.textViewEnglish.setText(word.getWord());
holder.textViewChinese.setText(word.getChineseMeaning());
}
@Override
public int getItemCount() {
return allWords.size(); //返回列表数据个数
}
static class MyViewHolder extends RecyclerView.ViewHolder {
TextView textViewNumber,textViewEnglish,textViewChinese;
public MyViewHolder(@NonNull View itemView) { //自带View类型的itemView
super(itemView);
textViewNumber = itemView.findViewById(R.id.textViewNumber);
textViewEnglish = itemView.findViewById(R.id.textViewEnglish);
textViewChinese = itemView.findViewById(R.id.textViewChinese);
}
}
}
- 在MainActivity中添加变量
import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProvider;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import java.util.List;
public class MainActivity extends AppCompatActivity {
Button buttonInsert,buttonUpdate,buttonDelete,buttonClear;
WordViewModel wordViewModel;
RecyclerView recyclerView;
MyAdapter myAdapter;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = findViewById(R.id.recyclerView);
myAdapter = new MyAdapter();
recyclerView.setLayoutManager(new LinearLayoutManager(this)); //创建一个一维线性列表，二维则是GridLayoutManager
recyclerView.setAdapter(myAdapter);
wordViewModel = new ViewModelProvider(this).get(WordViewModel.class);
//LiveData观察变动呼叫onchange函数，完成界面自动刷新
wordViewModel.getAllWordsLive().observe(this, new Observer<List<Word>>() {
@Override
public void onChanged(List<Word> words) {
myAdapter.setAllWords(words);
myAdapter.notifyDataSetChanged(); //数据变动通知视图
}
});
buttonInsert = findViewById(R.id.buttonInsert);
buttonClear = findViewById(R.id.buttonClear);
buttonDelete = findViewById(R.id.buttonDelete);
buttonUpdate = findViewById(R.id.buttonUpdate);
//插入
buttonInsert.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String[] english = {
"Hello",
"World",
"Android",
"Studio",
"Google",
"Project",
"Database",
"Recycler",
"View",
"String",
"Value",
"Integer"
};
String[] chinense = {
"你好",
"世界",
"安卓系统",
"工作室",
"谷歌",
"项目",
"数据库",
"回收站",
"视图",
"字符串",
"价值",
"整数类型"
};
for (int i = 0;i <english.length;i++) {
wordViewModel.insertWords(new Word(english[i],chinense[i]));
}
}
});
//清空
buttonClear.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
wordViewModel.clearWords();
}
});
//删除
buttonDelete.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Word word = new Word("",""); //删除只与id有关，内容无所谓
word.setId(90); //根据ID修改对应的表单名
wordViewModel.deleteWords(word);
}
});
//修改
buttonUpdate.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Word word = new Word("Android","安卓");
word.setId(90); //根据ID修改对应的表单名
wordViewModel.updateWords(word);
}
});
}
}
- 运行程序如图：
CardView的使用
依旧需要添加依赖：
- 创建一个新的界面布局，并编辑卡片界面layout：
<?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="wrap_content"
android:orientation="vertical">
<androidx.cardview.widget.CardView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_begin="55dp"
app:layout_constraintGuide_percent="0.1" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_begin="55dp"
app:layout_constraintGuide_percent="0.85" />
<TextView
android:id="@+id/textViewNumber"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/guideline4"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:text="1" />
<TextView
android:id="@+id/textViewEnglish"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:text="TextView"
android:textSize="24sp"
app:layout_constraintBottom_toTopOf="@+id/textViewChinese"
app:layout_constraintEnd_toStartOf="@+id/guideline5"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="@+id/guideline4"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/textViewChinese"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="@+id/textViewEnglish"
app:layout_constraintTop_toBottomOf="@+id/textViewEnglish" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.cardview.widget.CardView>
</LinearLayout>
- 改变适配器MyAdapter的itemView显示：
View itemView = layoutInflater.inflate(R.layout.cell_card,parent,false); //卡片模式界面
- 运行显示界面如下：
做一个界面显示切换按钮，点击按钮进行普通与卡片布局的切换显示
- 界面中做一个switch开关（多余的更新按钮和据项删除按钮在此没用，删除掉）
<?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="wrap_content"
android:orientation="vertical">
<androidx.cardview.widget.CardView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:layout_marginEnd="8dp">
<androidx.constraintlayout.widget.ConstraintLayout
android:layout_width="match_parent"
android:layout_height="match_parent">
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_begin="55dp"
app:layout_constraintGuide_percent="0.1" />
<androidx.constraintlayout.widget.Guideline
android:id="@+id/guideline5"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:orientation="vertical"
app:layout_constraintGuide_begin="55dp"
app:layout_constraintGuide_percent="0.85" />
<TextView
android:id="@+id/textViewNumber"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toStartOf="@+id/guideline4"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
tools:text="1" />
<TextView
android:id="@+id/textViewEnglish"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="8dp"
android:layout_marginTop="8dp"
android:text="TextView"
android:textSize="24sp"
app:layout_constraintBottom_toTopOf="@+id/textViewChinese"
app:layout_constraintEnd_toStartOf="@+id/guideline5"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="@+id/guideline4"
app:layout_constraintTop_toTopOf="parent" />
<TextView
android:id="@+id/textViewChinese"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginBottom="8dp"
android:text="TextView"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintStart_toStartOf="@+id/textViewEnglish"
app:layout_constraintTop_toBottomOf="@+id/textViewEnglish" />
</androidx.constraintlayout.widget.ConstraintLayout>
</androidx.cardview.widget.CardView>
</LinearLayout>
- MainActivity中添加变量：
Switch aSwitch;
MyAdapter myAdapter1,myAdapter2;
- 在MyAdapter适配器中添加域
boolean useCardView; //是否使用卡片布局视图
在加载View中做更改
@Override
public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
/*
* 当创建ViewHolder时
* 从Layout文件中
* 加载View
* */
LayoutInflater layoutInflater = LayoutInflater.from(parent.getContext());
View itemView;
if (useCardView) { //实现加载不同视图
itemView = layoutInflater.inflate(R.layout.cell_card,parent,false); //卡片模式界面
} else {
itemView = layoutInflater.inflate(R.layout.cell_normal,parent,false); //普通模式界面
}
return new MyViewHolder(itemView);
}
- 在MainActivity中做修改：
import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.Observer;
import androidx.lifecycle.ViewModelProvider;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.CompoundButton;
import android.widget.Switch;
import android.widget.TextView;
import java.util.List;
public class MainActivity extends AppCompatActivity {
Button buttonInsert,buttonClear;
WordViewModel wordViewModel;
RecyclerView recyclerView;
Switch aSwitch;
MyAdapter myAdapter1,myAdapter2;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
recyclerView = findViewById(R.id.recyclerView);
myAdapter1 = new MyAdapter(false);
myAdapter2 = new MyAdapter(true);
recyclerView.setLayoutManager(new LinearLayoutManager(this)); //创建一个一维线性列表，二维则是GridLayoutManager
recyclerView.setAdapter(myAdapter1);
aSwitch = findViewById(R.id.switch1);
aSwitch.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener() {
@Override
public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
if (isChecked) {
recyclerView.setAdapter(myAdapter2);
} else {
recyclerView.setAdapter(myAdapter1);
}
}
});
wordViewModel = new ViewModelProvider(this).get(WordViewModel.class);
//LiveData观察变动呼叫onchange函数，完成界面自动刷新
wordViewModel.getAllWordsLive().observe(this, new Observer<List<Word>>() {
@Override
public void onChanged(List<Word> words) {
myAdapter1.setAllWords(words);
myAdapter1.notifyDataSetChanged(); //数据变动通知视图
myAdapter2.setAllWords(words);
myAdapter2.notifyDataSetChanged(); //数据变动通知视图
}
});
buttonInsert = findViewById(R.id.buttonInsert);
buttonClear = findViewById(R.id.buttonClear);
//插入
buttonInsert.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String[] english = {
"Hello",
"World",
"Android",
"Studio",
"Google",
"Project",
"Database",
"Recycler",
"View",
"String",
"Value",
"Integer"
};
String[] chinense = {
"你好",
"世界",
"安卓系统",
"工作室",
"谷歌",
"项目",
"数据库",
"回收站",
"视图",
"字符串",
"价值",
"整数类型"
};
for (int i = 0;i <english.length;i++) {
wordViewModel.insertWords(new Word(english[i],chinense[i]));
}
}
});
//清空
buttonClear.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
wordViewModel.clearWords();
}
});
}
}
- 运行显示如下，切换按钮实现卡片布局显示：
制作点击单项ItemView点击反馈
（区别于点击事件，只是单纯的反馈给用户确实点击了该项ItemView）
- 在cell单项布局中的根节点设置clickable选为true
- 在cell单项布局中的根节点设置background（普通布局与卡片布局均要操作）
完成点击时反馈波纹效果
此处卡片布局的波纹显示不在前面，做更改为前景设置
<androidx.cardview.widget.CardView
...
android:foreground="?selectableItemBackground"
...>
完成点击单项Item跳转在线搜索（类似api接口）
- 在适配器中绑定网易跳转的逻辑关联
@Override
public void onBindViewHolder(@NonNull final MyViewHolder holder, int position) {
//绑定逻辑上的关联
Word word = allWords.get(position);
holder.textViewNumber.setText(String.valueOf(position + 1));
holder.textViewEnglish.setText(word.getWord());
holder.textViewChinese.setText(word.getChineseMeaning());
holder.itemView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Uri uri = Uri.parse("http://dict.youdao.com/w/" + holder.textViewEnglish.getText() + "/#keyfrom=dict2.top");
Intent intent = new Intent(Intent.ACTION_VIEW);
intent.setData(uri);
holder.itemView.getContext().startActivity(intent);
}
});
}
点击单项词缀，完成网页翻译跳转：
2. 页面中设置点击符号（增加人性化设置）
Layout布局中添加图标（矢量图在res中创建并根据提示添加兼容性语句）
<ImageView
android:id="@+id/imageView2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="@+id/guideline5"
app:layout_constraintTop_toTopOf="parent"
app:srcCompat="@drawable/ic_keyboard_arrow_right_black_24dp" />
预览图如下：
扫一扫
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