Android使用Room操作SQLite数据库让其变得无比高效和简洁(进一步完善用RecyclerView显示数据库中的数据)

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Android 使用Room操作SQLite数据库让其变得无比高效和简洁(教程一)

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下一篇文章数据库版本的升级，迁移

Android 使用Room操作数据库进行数据库版本的升级和迁移

将其数据展示更换成RecyclerView
activity_main.xml代码如下:

<?xmlversion="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="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity"><androidx.recyclerview.widget.RecyclerView
        android:id="@+id/recycle_view"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_weight="1" /><LinearLayout
        android:layout_width="match_parent"
        android:layout_height="150dp"
        android:orientation="vertical"><LinearLayout
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:gravity="center"
            android:orientation="horizontal"><Button
                android:id="@+id/btn_insert"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="1"
                android:text="添加" /><Switch
                android:id="@+id/switch1"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:layout_marginLeft="20dp" /><Button
                android:id="@+id/btn_clear"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_marginLeft="50dp"
                android:layout_weight="1"
                android:text="清除" /></LinearLayout></LinearLayout></LinearLayout>

之后写RecyclerView的子布局，这里我们用两种布局第一种是正常显示的列表布局，第二种用卡片式布局用到了CardView
第一种布局item_word.xml，正常显示的列表布局

<?xmlversion="1.0"encoding="utf-8"?><LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="80dp"
    android:background="?selectableItemBackground"
    android:clickable="true"
    android:orientation="horizontal"><LinearLayout
        android:layout_width="0dp"
        android:layout_height="80dp"
        android:layout_weight="1"
        android:gravity="center"><TextView
            android:id="@+id/tv_id"
            android:layout_width="80dp"
            android:layout_height="80dp" /></LinearLayout><LinearLayout
        android:layout_width="0dp"
        android:layout_height="80dp"
        android:layout_weight="5"
        android:orientation="vertical"><TextView
            android:id="@+id/tv_english"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1" /><TextView
            android:id="@+id/tv_chinese"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:height="0dp" /></LinearLayout><LinearLayout
        android:layout_width="0dp"
        android:layout_height="80dp"
        android:layout_weight="1"
        android:gravity="center"><ImageView
            android:layout_width="50dp"
            android:layout_height="50dp"
            android:layout_marginRight="10dp"
            android:src="@drawable/ic_baseline_chevron_right_24" /></LinearLayout></LinearLayout>

第二种布局item_card.xml，卡片式布局

<?xmlversion="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="?selectableItemBackground"
    android:clickable="true"><androidx.cardview.widget.CardView
        android:layout_width="match_parent"
        android:layout_height="80dp"
        android:layout_marginStart="10dp"
        android:layout_marginTop="10dp"
        android:layout_marginEnd="10dp"><LinearLayout
            android:layout_width="match_parent"
            android:layout_height="80dp"
            android:orientation="horizontal"><LinearLayout
                android:layout_width="0dp"
                android:layout_height="match_parent"
                android:layout_weight="1"
                android:gravity="center"><TextView
                    android:id="@+id/tv_id"
                    android:layout_width="80dp"
                    android:layout_height="80dp"
                    android:gravity="center" /></LinearLayout><LinearLayout
                android:layout_width="0dp"
                android:layout_height="80dp"
                android:layout_weight="5"
                android:orientation="vertical"><TextView
                    android:id="@+id/tv_english"
                    android:layout_width="match_parent"
                    android:layout_height="0dp"
                    android:layout_weight="1" /><TextView
                    android:id="@+id/tv_chinese"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:layout_weight="1"
                    android:height="0dp" /></LinearLayout><LinearLayout
                android:layout_width="0dp"
                android:layout_height="80dp"
                android:layout_weight="1"
                android:gravity="center"><ImageView
                    android:layout_width="50dp"
                    android:layout_height="50dp"
                    android:src="@drawable/ic_baseline_chevron_right_24" /></LinearLayout></LinearLayout></androidx.cardview.widget.CardView></LinearLayout>

这两个我们都在最外层布局中加上了两个属性

android:background="?selectableItemBackground"
android:clickable="true"

加上这两个属性后，用户点击数据列表时，会有一个阴影的一个效果，使用户有更好的体验。
之后创建一个适配器MyAdapter，通过适配器把数据渲染到页面上面

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.MyViewHolder>{
    private List<Word> allWords= new ArrayList<>();
    boolean userCardView;

    public MyAdapter(boolean userCardView){
        this.userCardView= userCardView;}

    public void setAllWords(List<Word> allWords){
        this.allWords= allWords;}

    @NonNull
    @Override
    public MyViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType){
        View view;if(userCardView){
            view= LayoutInflater.from(parent.getContext()).inflate(R.layout.item_card, parent,false);}else{
            view= LayoutInflater.from(parent.getContext()).inflate(R.layout.item_word, parent,false);}return new MyViewHolder(view);}

    @Override
    public intgetItemCount(){return allWords.size();}

    @Override
    public void onBindViewHolder(@NonNull MyViewHolder holder, int position){
        Word word= allWords.get(position);
        holder.tv_id.setText(String.valueOf(position +1));
        holder.tv_english.setText(word.getWord());
        holder.tv_chinese.setText(word.getChineseMeaning());
        holder.itemView.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view){
                Uri uri= Uri.parse("https://m.youdao.com/dict?le=eng&q=" + holder.tv_english.getText());
                Intent intent= new Intent(Intent.ACTION_VIEW);
                intent.setData(uri);
                holder.itemView.getContext().startActivity(intent);}});}

    public class MyViewHolder extends RecyclerView.ViewHolder{
        public TextView tv_id;
        public TextView tv_english;
        public TextView tv_chinese;

        public MyViewHolder(@NonNull View itemView){
            super(itemView);
            tv_id= itemView.findViewById(R.id.tv_id);
            tv_english= itemView.findViewById(R.id.tv_english);
            tv_chinese= itemView.findViewById(R.id.tv_chinese);}}}

最后在MainActivity中调用适配器，把数据呈现个用户

public class MainActivity extends AppCompatActivity{
    private Button btn_insert, btn_clear, btn_update, btn_delete;
    private WordViewModel wordViewModel;
    private RecyclerView recycle_view;
    private MyAdapter myAdapter1, myAdapter2;
    private Switch switch1;

    @Override
    protected void onCreate(Bundle savedInstanceState){
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn_insert= findViewById(R.id.btn_insert);
        btn_clear= findViewById(R.id.btn_clear);
//        btn_update= findViewById(R.id.btn_update);
//        btn_delete= findViewById(R.id.btn_delete);
        switch1= findViewById(R.id.switch1);
        recycle_view= findViewById(R.id.recycle_view);
        LinearLayoutManager linearLayoutManager= new LinearLayoutManager(this);
        recycle_view.setLayoutManager(linearLayoutManager);

        myAdapter1= new MyAdapter(false);
        myAdapter2= new MyAdapter(true);
        switch1.setOnCheckedChangeListener(new CompoundButton.OnCheckedChangeListener(){
            @Override
            public void onCheckedChanged(CompoundButton compoundButton, boolean isChecked){if(isChecked){
                    recycle_view.setAdapter(myAdapter2);}else{
                    recycle_view.setAdapter(myAdapter1);}}});

        wordViewModel= ViewModelProviders.of(this).get(WordViewModel.class);

        wordViewModel.getAllWordsLive().observe(this, new Observer<List<Word>>(){
            @Override
            public void onChanged(List<Word> words){
                myAdapter1.setAllWords(words);
                myAdapter1.notifyDataSetChanged();
                myAdapter2.setAllWords(words);
                myAdapter2.notifyDataSetChanged();}});
        recycle_view.setAdapter(myAdapter1);
        btn_insert.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(Viewv){
                String[] english={"Hello","World","Android","Google","Studio","Project"
                        ,"DataBase","Recycler","View","String","Value","Integer"};
                String[] chinese={"你好","世界","安卓系统","谷歌公司","工作室","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++){
                    Word word1= new Word(english[i], chinese[i]);
                    wordViewModel.insertWords(word1);}}});
        btn_clear.setOnClickListener(new View.OnClickListener(){
            @Override
            public void onClick(View view){
//                wordDao.deleteAllWords();
                wordViewModel.deleteAllWords();}});}}

效果如图所示：

点击下方按钮可以实现切换布局样式的功能~ 持续更新Room操作数据库的相关知识！