如何利用 android 中的数据库数据利用 canvas

Question

我是 Android 的新手，我一直在努力绘制 canvas 矩形和文本，其中矩形的大小、文本和颜色取决于从MySql 数据库。

我设法在我的 Activity 中选择了数据，但我就是不知道如何将 MySql 数据传递给 ondraw() 方法以便我可以绘制使用数据的矩形和文本。

任何帮助将不胜感激。

public class MyTankActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        Intent intent = getIntent();
        int useridInt = intent.getIntExtra("userid", -1);
        String userid = useridInt+"";

        Response.Listener<String> responseListener = new Response.Listener<String>() {
            @Override
            public void onResponse(String response) {
                try {
                    JSONObject jsonResponse = new JSONObject(response);

                    int success = jsonResponse.getInt("success");
                    JSONArray tank_data = jsonResponse.getJSONArray("tank_data");

                    if (success == 1) {
                        int i;
                        for(i=0;i<tank_data.length();i++){
                           // Log.v("Result--", "" + tank_data.getString(i));

                            JSONObject tankObj = tank_data.getJSONObject(0);

                            String location = (String) tankObj.getString("Location");
                            String color = (String) tankObj.getString("Color");
                            String Level = (String) tankObj.getString("Level");
                        }
                    } else {
                        // No records found in database
                    }
                } catch (JSONException e) {
                    e.printStackTrace();
                }
            }
        };

        MyTankRequest myTankRequest = new MyTankRequest(userid, responseListener);
        RequestQueue queue = Volley.newRequestQueue(MyTankActivity.this);
        queue.add(myTankRequest);

        setContentView(new TankView(this));
    }
}

XML布局：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.nivelsonic.nivelsonic.MyTankActivity"
    android:background="#AEECFF">

    <com.nivelsonic.nivelsonic.TankView
        android:layout_width="match_parent"
        android:layout_height="match_parent" />

</RelativeLayout>

坦克视图class：

package com.nivelsonic.nivelsonic;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.View;

public class TankView extends View {

    private Paint _paintTank = new Paint();
    private Path _path = new Path();

    public TankView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
        init(null, 0);
    }

    public TankView(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
        // TODO Auto-generated constructor stub
        init(attrs, 0);
    }

    public TankView(Context context, AttributeSet attrs) {
        super(context, attrs);
        // TODO Auto-generated constructor stub
        init(attrs, 0);
    }

    private void init(AttributeSet attrs, int defStyle) {
        _paintTank.setColor(Color.RED);
        _paintTank.setAntiAlias(true);
        _paintTank.setStyle(Paint.Style.STROKE);
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        // canvas.drawText();
        // canvas.rect();
    }   
}

Answer 1

一条建议：

移动JSON数据到全局变量

public class MyTankActivity extends AppCompatActivity {

   String location;
   String color;
   String Level;
  //....

并使用 TankView 的不同构造函数更改 setContentView 以允许传递获取的数据：

  setContentView(new TankView(this, location, color, Level));

相应地修改TankView的构造函数，同时向TankView添加一些变量来存储这些值：

  public TankView(Context context, String loc, String color, String level) {
    super(context);
    init(null, 0);
    this.location = loc;// ... do the same with color/level
    ...
 }

获取数据后修改onDraw

@Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        //using this.Location, color, text
        // canvas.drawText();.
        // canvas.rect();
    }

如何利用 android 中的数据库数据利用 canvas

How to draw on canvas using database data in android

mysql

database

android

ondraw

android-canvas