android - 在 Android 上刷新 View 或 Activity

Question

我有 1 个从服务器(数据库)接收 json 对象的 Activity ，每个名为 View 的 Activity (TableLayout 但在 ScrollView 中)自动更新。但是当我删除数据库中的数据(从当前 Activity 或直接从数据库中)时，布局不会更新。

我尝试过使用removeView方法，再次调用setContentView并重新初始化布局，最后我使用了startActivity 和 finish 方法。但我认为，如果每 10 秒将它与类似 setInterval 方法(但在 Android 上)一起使用，那将很奇怪。

有人知道如何在用户没有注意到 View 已刷新的情况下刷新 View 或 Activity 吗？

感谢您的回复，如果我错了，请见谅。让我知道我犯的错误。我在 Google 上搜索了一整天，但没有找到解决方案。

我在测试和 Linux 操作系统模拟器上使用 Android 2.2，这是我的代码:

package com.player;

import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.entity.BufferedHttpEntity;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;

import com.maestro.Mylist.SideMenuClick;
import com.maestro.libs.Functions;
import com.maestro.libs.SQLiteDatabaseConnector;

import android.app.Activity;
import android.app.AlertDialog;
import android.app.Dialog;
import android.content.Context;
import android.content.DialogInterface;
import android.content.Intent;
import android.content.DialogInterface.OnCancelListener;
import android.database.Cursor;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.view.Window;
import android.view.WindowManager;
import android.view.ViewGroup.LayoutParams;
import android.widget.ImageButton;
import android.widget.ScrollView;
import android.widget.TableLayout;
import android.widget.TableRow;
import android.widget.TextView;
import android.widget.Toast;

public class Playlist extends Activity {
private int page = 0;
private TableLayout tblContainer;
private int totalPage;

private String selectedItemIndex;
private TableRow selectedItem;
private Drawable rowColor;

// info to request page
private String roomName;
private String serverAddress;
private String playerUsername;
private String layoutUsername;

private Bundle stateTmp;

/**
 * 
 */
public Playlist() {
    // TODO Auto-generated constructor stub
}


public void getSong(){
    this.tblContainer = new TableLayout(this);

    StringBuilder builder = new StringBuilder();
    HttpClient httpClient = new DefaultHttpClient();
    HttpGet httpGet = new HttpGet(this.serverAddress + "/index.php?m=playlist&a=list&room=" + this.roomName + 
            "&p=" + page + "&ax=ok");
    Functions.showAlert(this, this.serverAddress + "/index.php?m=playlist&a=list&room=" + this.roomName + 
            "&p=" + page + "&ax=ok");

    try{
        HttpResponse response = httpClient.execute(httpGet);
        // httpClient.notify();
        HttpEntity ht = response.getEntity();
        InputStream content = ht.getContent();
        BufferedReader reader = new BufferedReader(new InputStreamReader(content));
        String line;

        while ((line = reader.readLine()) != null) {
            builder.append(line);
        }

        try {
            JSONArray obj = new JSONArray(builder.toString());

            for(int i=1, j=0; i<obj.length(); i++, j++){
                TableRow tr = new TableRow(this);
                tr.setOnClickListener(new View.OnClickListener() {

                    @Override
                    public void onClick(View arg0) {
                        // TODO Auto-generated method stub
                        // Functions.showAlert(getRef(), arg0.getTag().toString());
                        selectedItem = (TableRow) arg0;
                        rowColor = arg0.getBackground();
                        arg0.setBackgroundColor(0xFFFFA500);

                        selectedItemIndex = arg0.getTag().toString();
                        showDialog(0);
                    }
                });

                if((j % 2) == 0){
                    tr.setBackgroundColor(0xff00ffff);
                }
                tr.setTag(obj.getJSONObject(i).getString("id"));

                TextView td = new TextView(this);
                td.setText(obj.getJSONObject(i).getString("songtitle"));
                td.setTextSize(30);
                td.setTextColor(0xff000000);
                tr.addView(td, 350, 40);

                TextView td2 = new TextView(this);
                td2.setText(obj.getJSONObject(i).getString("artist"));
                td2.setTextSize(30);
                td2.setTextColor(0xff000000);
                tr.addView(td2, 350, 40);

                this.tblContainer.addView(tr);
            }

        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }catch(ClientProtocolException cpe){
        Functions.showAlert(this, cpe.toString());

    }catch(IOException e){
        Functions.showAlert(this, e.toString());

    }

}


/**
 * 
 */
public void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated constructor stub
    super.onCreate(savedInstanceState);
    this.stateTmp = savedInstanceState;

    getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
    requestWindowFeature(Window.FEATURE_NO_TITLE);
    setTitle("Maestro - Playlist");
    setContentView(R.layout.playlist);

    // get room name(location)
    if(savedInstanceState == null){
        Bundle tmp = this.getIntent().getExtras();
        if(tmp != null){
            this.roomName = tmp.getString("room_name");
            this.serverAddress = tmp.getString("server_address");
            this.playerUsername = tmp.getString("player_username");
            this.layoutUsername = tmp.getString("layout_username");
        }
    }

    /*SideMenuClick changeMenu = new SideMenuClick();
    ImageButton sideMenuSonglist = (ImageButton) findViewById(R.id.songlist);
    sideMenuSonglist.setOnClickListener(changeMenu);

    ImageButton sideMenuKeyControl = (ImageButton) findViewById(R.id.keycontrol);
    sideMenuKeyControl.setOnClickListener(changeMenu);

    ImageButton sideMenuMylist = (ImageButton) findViewById(R.id.mylist);
    sideMenuMylist.setOnClickListener(changeMenu);

    getSong();
    ScrollView sc = (ScrollView) findViewById(R.id.listcontainer);
    sc.addView(this.tblContainer);

    TextView txt = (TextView) findViewById(R.id.pagedesc);
    txt.setText((this.page+1) + " / " + this.totalPage);
    txt.setTextColor(0xff000000);

    ImageButton next = (ImageButton) findViewById(R.id.next);
    next.setOnClickListener(changeMenu);

    ImageButton prev = (ImageButton) findViewById(R.id.prev);
    prev.setOnClickListener(changeMenu);*/

    drawLayout(true);
}

public void drawLayout(boolean isFirst){
    if(isFirst == true){
        // getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
        // requestWindowFeature(Window.FEATURE_NO_TITLE);
        // setTitle("Maestro - Playlist");
    }


    SideMenuClick changeMenu = new SideMenuClick();
    ImageButton sideMenuSonglist = (ImageButton) findViewById(R.id.songlist);
    sideMenuSonglist.setOnClickListener(changeMenu);

    ImageButton sideMenuKeyControl = (ImageButton) findViewById(R.id.keycontrol);
    sideMenuKeyControl.setOnClickListener(changeMenu);

    ImageButton sideMenuMylist = (ImageButton) findViewById(R.id.mylist);
    sideMenuMylist.setOnClickListener(changeMenu);

    getSong();
    ScrollView sc = (ScrollView) findViewById(R.id.listcontainer);
    sc.addView(this.tblContainer);

    TextView txt = (TextView) findViewById(R.id.pagedesc);
    txt.setText((this.page+1) + " / " + this.totalPage);
    txt.setTextColor(0xff000000);

    ImageButton next = (ImageButton) findViewById(R.id.next);
    next.setOnClickListener(changeMenu);

    ImageButton prev = (ImageButton) findViewById(R.id.prev);
    prev.setOnClickListener(changeMenu);
}

public Context getRef(){
    return this;
}

public void changeActivity(int layoutId){
    Intent newActivity = new Intent();
    newActivity.putExtra("room_name", this.roomName);
    newActivity.putExtra("server_address", this.serverAddress);
    newActivity.putExtra("player_username", this.playerUsername);
    newActivity.putExtra("layoyt_username", this.layoutUsername);

    if(R.id.songlist == layoutId){
        newActivity.setClass(this, ListSongs.class);
        startActivity(newActivity);

    }else if(R.id.keycontrol == layoutId){
        newActivity.setClass(this, KeyControl.class);
        startActivity(newActivity);

    }else if(R.id.mylist == layoutId){
        newActivity.setClass(this, Mylist.class);
        startActivity(newActivity);

    }else if(R.id.prev == layoutId){
        if(page > 0){
            page--;
        }

        ScrollView sc = (ScrollView) findViewById(R.id.listcontainer);
        sc.removeView(this.tblContainer);

        getSong();

        sc.addView(this.tblContainer);
        TextView txt = (TextView) findViewById(R.id.pagedesc);
        txt.setText((this.page+1) + " / " + this.totalPage);


    }else if(R.id.next == layoutId){
        if(this.page < this.totalPage){
            page++;
        }

        ScrollView sc = (ScrollView) findViewById(R.id.listcontainer);
        sc.removeView(this.tblContainer);

        getSong();

        sc.addView(this.tblContainer);

        TextView txt = (TextView) findViewById(R.id.pagedesc);
        txt.setText((this.page+1) + " / " + this.totalPage);
    }
}

protected Dialog onCreateDialog(int id){

    LayoutInflater inflater = (LayoutInflater) this.getSystemService(LAYOUT_INFLATER_SERVICE);
    View layout = inflater.inflate(R.layout.playlist_popup, (ViewGroup) findViewById(R.id.layout_root));

    ImageButton ib0 = (ImageButton) layout.findViewById(R.id.back);
    ib0.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View arg0) {
            // TODO Auto-generated method stub
            selectedItem.setBackgroundDrawable(rowColor);
            dismissDialog(0);
        }
    });

    ImageButton ib1 = (ImageButton) layout.findViewById(R.id.del);
    ib1.setOnClickListener(new View.OnClickListener(){
        public void onClick(View arg0){
            Toast.makeText(getRef(), selectedItemIndex, 60000);
            HttpClient ajax = new DefaultHttpClient();
            HttpGet httpGet = new HttpGet(serverAddress + "/index.php?m=playlist&a=del&room=" + roomName + "&to=" + playerUsername + 
                    "&username=" + layoutUsername + "&id=" + selectedItemIndex);

            //Functions.showAlert(getRef(), serverAddress + "/index.php?m=playlist&a=del&room=" + roomName + "&to=" + playerUsername + 
            //      "&username=" + layoutUsername + "&id=" + selectedItemIndex);
            try {
                ajax.execute(httpGet);
            } catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            selectedItem.setBackgroundDrawable(rowColor);

            dismissDialog(0);

            // ScrollView sc = (ScrollView) findViewById(R.id.listcontainer);
            // sc.removeView(tblContainer);
            // sc.removeAllViewsInLayout();
            // sc.destroyDrawingCache();
            // tblContainer.removeAllViewsInLayout();
            // setContentView(R.layout.playlist);
            // setContentView(R.layout.playlist);
            // drawLayout(false);
            Intent newActivity = new Intent();
            newActivity.putExtra("room_name", roomName);
            newActivity.putExtra("server_address", serverAddress);
            newActivity.putExtra("player_username", playerUsername);
            newActivity.putExtra("layoyt_username", layoutUsername);
            newActivity.setClass(getRef(), Playlist.class);
            startActivity(newActivity);
            finish();

            // getSong();
            // sc = (ScrollView) findViewById(R.id.listcontainer);
            // tblContainer = new TableLayout(getRef());
            // sc.addView(tblContainer);
        }
    });

    ImageButton ib2 = (ImageButton) layout.findViewById(R.id.top);
    ib2.setOnClickListener(new View.OnClickListener(){
        public void onClick(View arg0){
            Toast.makeText(getRef(), selectedItemIndex, 60000);
            HttpClient ajax = new DefaultHttpClient();
            HttpGet httpGet = new HttpGet(serverAddress + "/index.php?m=playlist&a=top&room=" + roomName + "&to=" + playerUsername + 
                    "&username=" + layoutUsername + "&id=" + selectedItemIndex);

            try {
                ajax.execute(httpGet);
            } catch (ClientProtocolException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

            selectedItem.setBackgroundDrawable(rowColor);

            dismissDialog(0);

            ScrollView sc = (ScrollView) findViewById(R.id.listcontainer);
            sc.removeView(tblContainer);
            tblContainer = new TableLayout(getRef());

            getSong();

            sc.addView(tblContainer);
        }
    });


    layout.setLayoutParams(new LayoutParams(170, 90));
    layout.setMinimumWidth(0);

    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setView(layout);
    AlertDialog alertDialog = builder.create();
    alertDialog.setCancelable(true);
    alertDialog.setOnCancelListener(new OnCancelListener(){

        @Override
        public void onCancel(DialogInterface arg0) {
            // TODO Auto-generated method stub
            selectedItem.setBackgroundDrawable(rowColor);
            dismissDialog(0);
        }});

    return alertDialog;
}

public class SideMenuClick implements View.OnClickListener{

    @Override
    public void onClick(View arg0) {
        // TODO Auto-generated method stub
        // changeList();
        changeActivity(arg0.getId());
    }

}

}

Answer 1

Android 中的 View 有一个 Invalidate 和 PostInvalidate 方法，它们会在某个时候调用 OnDraw 方法。

因此，如果您用一些数据填充了一个 View ，您可以通过调用这两者之一使其重绘。