我已经创建了一个应用,但是当我在调用setContentView(R.layout.points)
@Override
protected void onCreate(Bundle savedInstanceState)
{
requestWindowFeature(Window.FEATURE_NO_TITLE);
super.onCreate(savedInstanceState);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.points);
final CanvasView canvas = (CanvasView) findViewById(R.id.signature_canvas);
// setContentView(R.layout.activity_main);
// addTouchListener();
}
CanvasView.java
package com.example.android.touchview;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;
import java.util.List;
/**
* Created by Vikas on 7/26/2016.
*/
public class CanvasView extends View
{
private Paint mPaint = new Paint();
DbActivity db =new DbActivity();
List mPts=db.getData();
float [] points =new float[mPts.size()];
public CanvasView(Context context,AttributeSet attributeSet)
{
super(context,attributeSet);
// Paint paint = mPaint;
//canvas.translate(10, 10);
//canvas.drawColor(Color.WHITE);
//mPaint.setColor(Color.RED);
mPaint.setStrokeWidth(0);
mPaint.setAntiAlias(true);
mPaint.setColor(Color.BLACK);
mPaint.setStrokeWidth(3);
}
@Override
protected void onDraw(Canvas canvas)
{
super.onDraw(canvas);
canvas.drawPoints(points, mPaint);
}
}
这是我的xml文件
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/points_canvas"
android:layout_width="match_parent"
android:layout_height="match_parent">
<com.example.android.touchview.CanvasView
android:id="@+id/signature_canvas"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
</FrameLayout>
DbActivity.java
package com.example.android.touchview;
/**
* Created by Vikas on 7/20/2016.
*/
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.TextView;
import java.sql.SQLException;
import java.util.ArrayList;
public class DbActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_db);
TextView tv = (TextView) findViewById(R.id.SQLinfo);
DataBase db = new DataBase(this);
try {
db.open();
ArrayList<Float> data = db.getData();
db.close();
// data.toString();
tv.setText(data.toString());
//Log.d("THE DATA IS ", "+ data.get(i)");
/* for(int i=0;i<data.size();i++)
{
tv.setText(data.get(i).toString());
Log.d("hi", "data[i]");
}*/
} catch (SQLException e) {
e.printStackTrace();
}
}
public ArrayList<Float> getData()
{
ArrayList<Float> data= new ArrayList<>();
DataBase db = new DataBase(this);
try {
db.open();
data = db.getData();
db.close();
} catch (SQLException e)
{
e.printStackTrace();
}
return data;
}
}
修改了Canvas.java
package com.example.android.touchview;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;
import java.util.List;
/**
* Created by Vikas on 7/26/2016.
*/
public class CanvasView extends View
{
private Paint mPaint = new Paint();
float[] points ;
public CanvasView(Context context,AttributeSet attributeSet)
{
super(context,attributeSet);
DbActivity db =new DbActivity();
List mPts=db.getData();
points =new float[mPts.size()];
// Paint paint = mPaint;
//canvas.translate(10, 10);
//canvas.drawColor(Color.WHITE);
//mPaint.setColor(Color.RED);
}
@Override
protected void onDraw(Canvas canvas)
{
super.onDraw(canvas);
mPaint.setStrokeWidth(0);
mPaint.setAntiAlias(true);
mPaint.setColor(Color.BLACK);
mPaint.setStrokeWidth(3);
canvas.drawPoints(points, mPaint);
}
}
Database.java
package com.example.android.touchview;
/**
* Created by Vikas on 7/20/2016.
*/
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.util.Log;
import java.sql.SQLException;
import java.util.ArrayList;
public class DataBase
{
public static final String KEY_ROWID = "_id";
public static final String KEY_X = "X";
public static final String KEY_Y = "Y";
private static final String DATABASE_NAME = "Details";
private static final String DATABASE_TABLE = "DetailsTable";
private static final int DATABASE_VERSION = 1;
private DbHelper ourHelper;
private final Context ourContext;
private SQLiteDatabase ourDatabase;
private static class DbHelper extends SQLiteOpenHelper {
public DbHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
// TODO Auto-generated constructor stub
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
db.execSQL("CREATE TABLE " + DATABASE_TABLE + " (" + KEY_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
KEY_X + " TEXT, " + KEY_Y + " TEXT);");
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE);
onCreate(db);
}
}
public DataBase(Context c) {
ourContext = c;
}
public DataBase open() throws SQLException {
ourHelper = new DbHelper(ourContext);
ourDatabase = ourHelper.getWritableDatabase();
return this;
}
public void close() {
ourHelper.close();
}
public long createEntry(String x, String y) {
ContentValues cv = new ContentValues();
cv.put(KEY_X, x);
cv.put(KEY_Y, y);
return ourDatabase.insert(DATABASE_TABLE, null, cv);
}
public ArrayList<Float> getData() {
ourDatabase = ourHelper.getReadableDatabase();
Point p = new Point();
ArrayList<Float> dataPoints = new ArrayList<>();
String[] col = new String[]{KEY_ROWID, KEY_X, KEY_Y};
Cursor c = ourDatabase.query(DATABASE_TABLE, col, null, null, null, null, null);
float[] array = new float[c.getCount()];
float[] array1 = new float[c.getCount()];
int i = 0;
if (c.moveToFirst())
{
do {
float x = c.getFloat(c.getColumnIndex("X"));
p.setX(x);
dataPoints.add(p.getX());
float y = c.getFloat(c.getColumnIndex("Y"));
p.setY(y);
dataPoints.add(p.getY());
array[i] = x;
array1[i] = y;
i++;
} while (c.moveToNext());
}
Log.d("hi", "getData() called");
return dataPoints;
}
}
我收到此错误
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.example.android.touchview/com.example.android.touchview.MainActivity}: android.view.InflateException: Binary XML file line #7: Error inflating class com.example.android.touchview.CanvasView
答案 0 :(得分:0)
以下行似乎导致错误:
DbActivity db =new DbActivity();
List mPts=db.getData();
float [] points =new float[mPts.size()];
首先,将所有初始化移至构造函数方法并避免这种初始化方式。其次,你不应该实例化一个活动。
建议将所有数据库级逻辑移动到名为DbHelper
的类,并在方法范围中使用它。这样的事情看起来很好:
DbHelper db;
List mPts;
float [] points;
public CanvasView(Context context,AttributeSet attributeSet)
{
super(context,attributeSet);
db = new DbHelper(...);
mPts = new ArrayList<>();
points = new float[...];
...
}