[安卓] 数据库为Android - P3改善应用程序

四月 28, 2017 nguyenvanquan7826 TUT数据库的Android 8 回复

在 2 幸运的是，我们有 创建数据库 和 齐全的接口设计 应用. 在这一点上，我们不断完善景点

注意:
这个系列的剧本我会用英文写. 然而，这是我的英文写作风格“译自越南”那么你会很容易跟进.
这里: Android的工作室 1.2.2
Android的SDK 5.1.1
闵SDK: 4.0 (安卓 4.0 以上将被用于应用程序)
但是，你绝对可以做Eclipse和Android的下

步 1: 创建适配器项目

我们将通过RecyclerViewHolder创建项目适配器RecyclerView, 它会帮助我们的名单顺畅, 优化.

package cachhoc.net.tut.demodatabase;

import android.content.Context;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.widget.LinearLayout;
import android.widget.TextView;

import java.util.ArrayList;
import java.util.List;

public class ItemNoteAdapter extends RecyclerView.Adapter<ItemNoteAdapter.RecyclerViewHolder> {

    // list of note
    private List<Note> list = new ArrayList<Note>();
    private Context context;

    public ItemNoteAdapter(Context context, List<Note> list) {
        this.context = context;
        this.list = list;
    }

    @Override
    public int getItemCount() {
        return list.size();
    }

    /**
     * connect to item view
     */
    @Override
    public RecyclerViewHolder onCreateViewHolder(ViewGroup viewGroup, int position) {
        LayoutInflater inflater = LayoutInflater.from(viewGroup.getContext());
        View itemView = inflater.inflate(R.layout.item, viewGroup, false);
        return new RecyclerViewHolder(itemView);
    }

    /**
     * set data for item
     */
    @Override
    public void onBindViewHolder(RecyclerViewHolder viewHolder, int position) {
        Note note = list.get(position);
        viewHolder.tvTitle.setText(note.getTitle());
        viewHolder.tvContent.setText(note.getContent());
    }


    public void addItem(int position, Note note) {
        list.add(position, note);
        notifyItemInserted(position);
    }

    public void removeItem(int position) {
        list.remove(position);
        notifyItemRemoved(position);
    }

    /**
     * ViewHolder for item view of list
     */

    public class RecyclerViewHolder extends RecyclerView.ViewHolder implements
            OnClickListener {

        public LinearLayout container;
        public TextView tvTitle;
        public TextView tvContent;

        public RecyclerViewHolder(View itemView) {
            super(itemView);

            container = (LinearLayout) itemView.findViewById(R.id.item_container);
            tvTitle = (TextView) itemView.findViewById(R.id.tv_title);
            tvContent = (TextView) itemView.findViewById(R.id.tv_content);

            container.setOnClickListener(this);
        }

        // click item then display note
        @Override
        public void onClick(View v) {
            MainActivity.showNote(context, list.get(getPosition()).getId());
        }
    }
}

以上我必须调用显示音符showNote的方法点击时 1 项目. 该方法是用类MainActivity.

步 2: 建设MainActivity

package cachhoc.net.tut.demodatabase;

import android.content.Context;
import android.content.Intent;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.view.View;

import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

    private ItemNoteAdapter adapter;
    private List<Note> listNote = new ArrayList<>();

    private Context context;

    private DatabaseHelper db;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        context = this;

        db = new DatabaseHelper(context);

        connectView();
    }

    /**
     * connect java with xml view
     */
    private void connectView() {

        // find Float Action Button
        findViewById(R.id.fab).setOnClickListener(this);

        RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rv_note);

        // If the size of views will not change as the data changes.
        recyclerView.setHasFixedSize(true);

        // Setting the LayoutManager.
        RecyclerView.LayoutManager layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);

        // Setting the adapter.
        adapter = new ItemNoteAdapter(context, listNote);
        recyclerView.setAdapter(adapter);
    }

    /**
     * update list note when resume (open app or finish NoteActivity)
     */
    public void onResume() {
        super.onResume();
        updateListNote();
    }

    /**
     * select all note from database and set to ls
     * use for loop to add into listNote.
     * We must add all item in ls into listNote then adapter can update
     * we add reverse ls to show new note at top of list
     */
    private void updateListNote() {
        // clear old list
        listNote.clear();
        // add all notes from database, reverse list
        ArrayList<Note> ls = db.getListNote("SELECT * FROM " + DatabaseHelper.TABLE_NOTE);

        // reverse list
        for (int i = ls.size() - 1; i >= 0; i--) {
            listNote.add(ls.get(i));
        }

        adapter.notifyDataSetChanged();
    }

    /**
     * display note have id
     */
    public static void showNote(Context context, long id) {
        Intent intent = new Intent(context, NoteActivity.class);

        // send id to NoteActivity
        intent.putExtra(NoteActivity.ID, id);

        context.startActivity(intent);
    }

    @Override
    public void onClick(View v) {
        switch (v.getId()) {
            case R.id.fab:
                showNote(context, NoteActivity.NEW_NOTE);
                break;
            default:
                break;
        }
    }
}

代码也是很容易理解. 只要 2 您可以共享下面的担忧:

  • 为了能够解决它需要设置一个布局RecyclerView. 在他的代号为LinearLayoutManager同时RecyclerView名单将作为平滑的ListView. 如果使用，这将是一个网格GridLayoutManager.

  • 仲TA选择的ArrayList 从分配给LS数据库. 然后，将这些元素复制到相当listNote 未分配的listNote = LS 因为那时listNote将采用不同的存储区域 (LS的存储器) 使得适配器不能被更新. 我们也反向LS分配给listNote，因为我希望把音符写在列表的顶部后，.

步 3: 创建注释起草NoteActivity

package cachhoc.net.tut.demodatabase;

import android.content.Context;
import android.content.DialogInterface;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.text.TextUtils;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.EditText;
import android.widget.Toast;
import android.support.v7.app.AlertDialog;


public class NoteActivity extends AppCompatActivity {

    /**
     * if action is add new note, it will init by NEW_NOTE
     */
    public static final long NEW_NOTE = -1;

    /**
     * key for get id note from other activity to display note
     */
    public static final String ID = "ID";

    /**
     * to edit, add,... note from database
     */
    private DatabaseHelper db;

    /**
     * note curren
     */
    private Note note;

    private EditText editTitle;
    private EditText editContent;

    private Context context;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_note);

        context = this;

        db = new DatabaseHelper(context);

        connectView();
        getInfo();
    }

    /**
     * conect with xml view
     */
    private void connectView() {
        editTitle = (EditText) findViewById(R.id.edit_title);
        editContent = (EditText) findViewById(R.id.edit_content);
    }

    /**
     * get info note to display
     */
    private void getInfo() {
        long id = getIntent().getLongExtra(ID, NEW_NOTE);

        // not new note then find note from database by id of note
        if (id != NEW_NOTE) {
            String sql = "SELECT * FROM " + DatabaseHelper.TABLE_NOTE + " WHERE " + DatabaseHelper.KEY_ID_NOTE + " = " + id;
            note = db.getNote(sql);
        }
        
        if (note != null) {
            editTitle.setText(note.getTitle());
            editContent.setText(note.getContent());
        } else {
            editTitle.setText("");
            editContent.setText("");
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_note, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
            case R.id.menu_save:
                save();
                break;
            case R.id.menu_delete:
                delete();
                break;
            default:
                break;
        }
        return super.onOptionsItemSelected(item);
    }

    /**
     * get title and content of note, if they empty then finish
     * if they not empty then check note is null?
     * if note is null (create new note), we will create note and insert into database
     * if note not null then we update note
     * after save we finish activity
     */
    private void save() {

        String title = editTitle.getText().toString().trim();
        String content = editContent.getText().toString().trim();

        String notify = null;

        if (TextUtils.isEmpty(title) && TextUtils.isEmpty(content)) {
            notify = "note empty, don't save!";
        } else {
            // new note
            if (note == null) {
                Note note = new Note();
                note.setTitle(title).setContent(content);
                if (db.insertNote(note) > 0) {
                    notify = "add success!";
                } else {
                    notify = "add fail!";
                }
            } else { // update note
                note.setTitle(title).setContent(content);
                if (db.updateNote(note)) {
                    notify = "update success!";
                } else {
                    notify = "update fail!";
                }
            }
        }

        Toast.makeText(context, notify, Toast.LENGTH_SHORT).show();
        finish();
    }

    /**
     * get title and content of note, if they empty then finish
     * if they not empty then show dialog to show question delete
     * if select no delete then close dialog
     * if select delete then delete note
     */
    private void delete() {
        String title = editTitle.getText().toString().trim();
        String content = editContent.getText().toString().trim();

        if (TextUtils.isEmpty(title) && TextUtils.isEmpty(content)) {
            finish();
        } else {
            final AlertDialog.Builder builder = new AlertDialog.Builder(this, R.style.AppCompatAlertDialogStyle);
            builder.setTitle(R.string.delete).setIcon(R.mipmap.ic_launcher)
                    .setMessage("Do you want delete note?");
            builder.setPositiveButton(R.string.no, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                }
            });
            builder.setNegativeButton(R.string.yes, new DialogInterface.OnClickListener() {
                @Override
                public void onClick(DialogInterface dialog, int which) {
                    deleteNote();
                }
            });
            builder.show();
        }
    }

    /**
     * check note is null?
     * if is null then finish
     * if note not null then delete in database and finish
     */
    private void deleteNote() {
        if (note != null) {
            String where = DatabaseHelper.KEY_ID_NOTE + " = " + note.getId();
            String notify = "delete success!";

            if (!db.deleteNote(where)) {
                notify = "delete failt!";
            }
            Toast.makeText(context, notify, Toast.LENGTH_SHORT).show();
        }
        finish();
    }

    /**
     * click back button on phone
     */
    @Override
    public void onBackPressed() {
        save();
    }

}

在NoteActivity, 当它开始被发送到该ID的意图. NEU ID = NEW_NOTE (是 -1) 这意味着创建一个新的笔记, 我们的setText为editTitle和editContent空字符串. 否则，我们将注意从数据库ID并显示在.

代码完全乱了套. 我们希望你能完成申请.

您是当场就可以 下载项目DemoDatabase

部分 4 接下来，我将指导您如何更新数据库，如果不改变目前的应用程序错误.

在本教程的帖子 数据库的Andr​​oid仲 由 nguyenvanquan7826