7步完成使用LitePal数据库

 

第一步：在项目的app/build.gradle加上，连接上litepal库

dependencies {
 implementation 'org.litepal.android:core:2.0.0'
}

第二步：新建一个MyApplication.java，初始化litepal.initialize

package com.example.administrator.WeChats;

import android.app.Application;

import org.litepal.LitePal;

public class MyApplication extends Application {
    @Override
    public  void onCreate()
    {
        super.onCreate();
        LitePal.initialize(this);
    }
}

第三步：然后在androidManifest.xml，设置application：Android：name；为了正常使用litepal

第四步，新建Friend类

package com.example.administrator.WeChats.data;

import org.litepal.crud.LitePalSupport;

public class Friends extends LitePalSupport{
    private int id;
    private String name;
    private int number;
    private boolean sex;

    public int getId() {
        return id;
    }
    public String getName() {
        return name;
    }
    public int getNumber() {
        return number;
    }
    public boolean isSex() {
        return sex;
    }
    public void setId(int id){
        this.id=id;
    }
    public void setName(String name) {
        this.name = name;
    }
    public void setNumber(int number) {
        this.number = number;
    }
    public void setSex(boolean sex) {
        this.sex = sex;
    }
}

第五步：新建一个DataAdapter

package com.example.administrator.WeChats;
        import java.util.List;
        import android.content.Context;
        import android.support.annotation.NonNull;
        import android.text.TextUtils.TruncateAt;
        import android.view.Gravity;
        import android.view.View;
        import android.view.ViewGroup;
        import android.widget.ArrayAdapter;
        import android.widget.LinearLayout;
        import android.widget.TextView;

public class DataArrayAdapter extends ArrayAdapter> {

    public DataArrayAdapter(Context context, int textViewResourceId, List> objects) {
        super(context, textViewResourceId, objects);
    }

    @Override
    public @NonNull View  getView(int position, View convertView,@NonNull ViewGroup parent) {
        List dataList = getItem(position);
        LinearLayout layout;
        if (convertView == null) {
            layout = new LinearLayout(getContext());
        } else {
            layout = (LinearLayout) convertView;
        }
        layout.removeAllViews();
        int width = Utility.dp2px(getContext(), 100);
        int height = Utility.dp2px(getContext(), 30);
        for (String data : dataList) {
            LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(width, height);
            TextView textView = new TextView(getContext());
            textView.setText(data);
            textView.setSingleLine(true);
            textView.setEllipsize(TruncateAt.END);
            textView.setGravity(Gravity.CENTER_VERTICAL);
            layout.addView(textView, params);
        }
        return layout;
    }

}

第六步：新建做数据添加的活动DataActivity

package com.example.administrator.WeChats.Activity;
import android.Manifest;
import android.content.Context;
import android.content.Intent;
import android.content.pm.PackageManager;
import android.database.Cursor;
import android.net.Uri;
import android.os.Build;
import android.provider.MediaStore;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v4.content.FileProvider;
import android.support.v7.app.ActionBar;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
import com.example.administrator.WeChats.DataArrayAdapter;
import com.example.administrator.WeChats.R;
import com.example.administrator.WeChats.data.Friends;
import org.litepal.LitePal;
import org.litepal.tablemanager.Connector;
import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class DataActivity extends AppCompatActivity implements View.OnClickListener
{
    public static void actionStart(Context context) {
        Intent intent=new Intent(context,DataActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
        context.startActivity(intent);
    }

    public static int i=0;
    private ListView mDataListView;
    private DataArrayAdapter mAdapter;
    private List> mList = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_data);
        ActionBar actionBar=getSupportActionBar();
        if(actionBar !=null)
            actionBar.setDisplayHomeAsUpEnabled(true);

        Button createDatabase = findViewById(R.id.createdb);
        Button addData =findViewById(R.id.addData);
        Button deleteData=findViewById(R.id.deleteData);
        createDatabase.setOnClickListener(this);
        addData.setOnClickListener(this);
        deleteData.setOnClickListener(this);

        mDataListView = findViewById(R.id.data_list_view);
        mAdapter = new DataArrayAdapter(this, 0, mList);
        mDataListView.setAdapter(mAdapter);
        populateDataFromDB();
    }

    @Override
    public void onClick(View v) {
        Friends f = new Friends();
        switch (v.getId()) {
            case R.id.createdb:
            {
                LitePal.getDatabase();
            }break;
            case R.id.addData:
            {
             try {
                    i++;
                    f.setId(1995);
                    f.setName("old friends: "+i);
                    f.setNumber(i);
                    f.setSex(true);
                    f.save();
                    refreshListView(f.getId(), f.getName(),f.getNumber(), f.isSex());
                }catch (Exception e){
                    e.printStackTrace();
                    Toast.makeText(this,"addData error",Toast.LENGTH_SHORT).show();
                }
            }break;
            case R.id.deleteData:
                try {
                     LitePal.delete(Friends.class,i--);
                    refreshListView(f.getId(), f.getName(),f.getNumber(), f.isSex());
                } catch (Exception e) {
                    e.printStackTrace();
                }break;
            default :break;
        }
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case android.R.id.home:
            {
                finish();
            }break;
            default :break;
        }
        return super.onOptionsItemSelected(item);
    }

//----------填充来自数据库中的数据---------------------
    private void populateDataFromDB() {
        new Thread(new Runnable() {
            @Override
            public void run() {
                mList.clear();
                List columnList = new ArrayList();
                columnList.add("id");
                columnList.add("name");
                columnList.add("number");
                columnList.add("sex");
                mList.add(columnList);
                Cursor cursor = null;
                try {
                    cursor = Connector.getDatabase().rawQuery("select * from friend order by id",null);
                    if (cursor.moveToFirst()) {
                        do {
                           long id = cursor.getLong(cursor.getColumnIndex("id"));
                            String name = cursor.getString(cursor.getColumnIndex("name"));
                           int number = cursor.getInt(cursor.getColumnIndex("number"));
                           int sex = cursor.getInt(cursor.getColumnIndex("sex"));
                            List stringList = new ArrayList();
                            stringList.add(String.valueOf(id));
                            stringList.add(name);
                            stringList.add(String.valueOf(number));
                            stringList.add(String.valueOf(sex));
                            mList.add(stringList);
                        } while (cursor.moveToNext());
                    }
                } catch (Exception e) {
                    e.printStackTrace();
                } finally {
                    if (cursor != null) {
                        cursor.close();
                    }
                    runOnUiThread(new Runnable() {
                        @Override
                        public void run() {
                            mAdapter.notifyDataSetChanged();//重绘当前可见区域
                        }
                    });
                }
            }
        }).start();
    }

    private void refreshListView(long id, String name, int number, boolean sex) {
        List stringList = new ArrayList();
        stringList.add(String.valueOf(id));
        stringList.add(name);
        stringList.add(String.valueOf(number));
        stringList.add(String.valueOf(sex));
        mList.add(stringList);
        mAdapter.notifyDataSetChanged();
        mDataListView.setSelection(mList.size());
    }
}

 第七步：布局activity_Data.xml

刚刚成功运行，后期优化了再来更新代码。