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已关闭8年。
因此，我在Java中有些菜鸟了，我正在尝试为Android开发一个应用程序。
Î出现一些错误，但我无法解决。谁能帮我找到问题所在？
这是我的mainActivity:
package com.example.w;
//import com.example.jkhgvcxz.R;
import views.DrawView;
import android.app.Activity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.Menu;
import android.view.MotionEvent;
import android.view.View;
import android.widget.RelativeLayout;
public class MainActivity extends Activity {
Ponto2D patual = new Ponto2D();
int contador = 0;
DrawView drawView;
View view2;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
RelativeLayout rl = (RelativeLayout) findViewById(R.id.rl);
RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(500, 500);
params.leftMargin = 50;
params.topMargin = 50;
drawView = new DrawView(this);
drawView.setBackgroundColor(Color.WHITE);
rl.addView(drawView, params);
drawView.setOnTouchListener(new View.OnTouchListener() {
// @Override
public boolean onTouch(View v, MotionEvent event) {
Ponto2D patual = new Ponto2D((int)event.getX(), (int)event.getY()); Reta r1 = new Reta (inicio, fim);
DrawView.ar[contador] =rl[];
inicio.X = \.X;
inicio.Y = fim.Y;
contador++;
if (event.getAction()== MotionEvent.ACTION_DOWN)
{
drawView.a=7;
drawView.antigox=drawView.X;
drawView.antigoy=drawView.Y;
drawView.X=event.getX();
drawView.Y=event.getY();
//drawView.draw();
drawView.desenhar_quadrado();}
return true;
}
});
}
public void btn(View v)
{
drawView.desenhar_quadrado();
}
public void btn_verde(View v)
{
drawView.paint.setColor(Color.GREEN);
}
public void btn_vermelho(View v)
{
drawView.paint.setColor(Color.RED);
}
public void btn_preto(View v)
{
drawView.paint.setColor(Color.BLACK);
}
public void btn_azul(View v)
{
drawView.paint.setColor(Color.BLUE);
}
public void btn_amarelo(View v)
{
drawView.paint.setColor(Color.YELLOW);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
}
我的Reta类(class):
package com.example.w;
public class Reta {
Ponto2D inicio;
Ponto2D fim;
int cor;
public Reta(Ponto2D p1, Ponto2D p2){
inicio = new Ponto2D(p1.x, p1.y);
fim = new Ponto2D(p2.x, p2.y);
}
}
我的DrawView类:
package views;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.view.View;
import com.example.w.Reta;
public class DrawView extends View {
public Paint paint = new Paint();
Reta ar[] = new Reta [10];
public int a;
public float antigox=0;
public float antigoy=0;
public float X=0;
public float Y=0;
public DrawView(Context context) {
super(context);
paint.setColor(Color.BLACK);
a=0;
}
public void desenhar_quadrado()
{
invalidate();
}
@Override
public void onDraw(Canvas canvas) {
for(int j=0; j<10; j++){
drawLine(ar[j].inicio.x, ar[j].inicio.y);
}
}
}
还有我的Ponto2D课:
package com.example.w;
public class Ponto2D {
int x;
int y;
public Ponto2D()
{
x = -1;
y = -1;
}
public Ponto2D(int x, int y)
{
this();
this.x = x;
this.y = y;
}
}
现在我有(44-50)
- The constructor Ponto2D(float, float) is undefined
- fim cannot be resolved to a variable
- inicio cannot be resolved to a variable
- line 47: Syntax error on token "[", Expression expected after this token
- Cannot refer to a non-final variable rl inside an inner class defined in a different method
- The field DrawView.ar is not visible
- The type of the expression must be an array type but it resolved to RelativeLayout
- fim cannot be resolved to a variable - inicio cannot be resolved to a variable.
同样在DrawView.java中，第34行我得到:
- The field Reta.inicio is not visible,
- The method drawLine(int, int) is undefined for the type DrawView
- The field Reta.inicio is not visible
- The field Ponto2D.x is not visible.
看这个
public class MainActivity extends Activity {
Ponto2D patual = new Ponto2D(); <---- here
//...
}
您从未在类中定义Ponto2D()构造函数。
添加一个
public Ponto2D()
{
x = -1;
y = -1;
}
public Ponto2D(int x, int y)
{
this();
this.x = x;
this.y = y;
}
第2部分:
public float X=0;
public float Y=0;
然后你这样做
Ponto2D patual = new Ponto2D(event.getX(), event.getY());
真的应该是
Ponto2D patual = new Ponto2D((int)event.getX(), (int)event.getY());
或者您将您的Ponto2D类重做为如下所示
public class Ponto2D
{
float x;
float y;
public Ponto2D ()
{
x=-1.0;
y=-1.0;
}
public Ponto2D(float x, float y)
{
this();
this.x = x;
this.y = y;
}
} //end of class
第3部分:
好的，我现在将描述每个错误。
构造函数Ponto2D(float，float)是不确定的-我们讨论了这一点。 fim无法解析为变量-您从未在MainActivity类中定义'fim'。您需要使用定义的值。我猜您想使用Reta类中的“fim”吗？在这种情况下...
Reta r1 =新Reta(inicio，FIM); 改成
Reta r1 = new Reta (new Ponto2D(), new Ponto2D());
要么
Reta r1 = new Reta (new Ponto2D(<your values>), new Ponto2D(<values again>));
inicio无法解析为变量
与上一个相同。 第47行: token “[”上的语法错误，此 token 后需要表达
DrawView.ar[contador] =rl[];
inicio.X = \.X;
inicio.Y = fim.Y;
这将永远不会编译儿子。我不知道您在尝试什么，但是我建议您收集关于此的想法:D
无法在不同方法中定义的内部类内引用非最终变量rl
这个很有趣。这意味着您无法定位rl，后者是在内部类的外部类中定义的。所以要解决它，只需交换一下
RelativeLayout rl = (RelativeLayout) findViewById(R.id.rl);
有了这个
final RelativeLayout rl = (RelativeLayout) findViewById(R.id.rl);
该错误有时很难修复，有时您只添加final，有时需要变量的最终副本，而另一些时候则需要真正地重组代码。幸运的是，这次添加了final即可。
字段DrawView.ar不可见打开您的DrawView类，看看这个
public class DrawView extends View {
public Paint paint = new Paint();
Reta ar[] = new Reta [10]; //offending line
public int a;
//...
所以要么像
public class DrawView extends View
{
public Paint paint = new Paint();
public Reta ar[] = new Reta [10];
//...
}
或生成 getter / setter 。
表达式的类型必须是数组类型，但已解析为RelativeLayout
一旦您对前面提到的想法有了想法，这一想法就会自动消失。相信我，我是一名工程师;)字段Reta.inicio不可见，
这是不言自明的...
公共(public)类Reta
{
公开的Ponto2D创意;
公共(public)Ponto2D fim；
公共(public)情报
//...
字段Reta.inicio不可见字段Ponto2D.x不可见。 看到了，这就是为什么您使用getter和setter而不直接从不同的类访问该类的字段的原因。
尝试像这样
public class Ponto2D
{
private int x; //2d plane shouldn't use floating coordinates.
private int y;
Ponto2D() { }; //ctor does nothing.
public Ponto2D(int x, int y)
{
this();
this.x = x;
this.y = y;
}
public int getX() { return x; }
public int getY() { return y; }
}
public class Reta
{
private Ponto2D inicio;
private Ponto2D fim;
private int cor;
Reta()
{
fin = new Ponta2D(); //might cause an error because it's not public
inicio = new Ponta2D(-1, -1); //this should be ok
}
public Reta(Ponto2D p1, Ponto2D p2)
{
//this.inicio = new Ponto2D(p1.getX()，p1.getY());//这真是胡扯
//this.fim = new Ponto2D(p2.getX()，p2.getY());
this.inicio = p1;
this.fim = p2;//let使用这些代替新对象。除非您想要新对象。
}
}
这种代码样式将为您提供一个避免此类错误的思路。
最后部分:
我将为您提供帮助，其余的如果您想以此为生，就必须自己弄清楚……您所犯的错误是学生级别的初学者编程错误，与实际无关Java或Android。您需要了解并知道如何解决这些问题的人，因为没有人会浪费时间为您定义 undefined reference ，并且像这样提出它甚至是很不礼貌的(这表明您甚至没有阅读代码)
无法对非静态字段DrawView.ar进行静态引用
好的，这是您做了什么:
public class DrawView extends View {
public Paint paint = new Paint();
Reta ar[] = new Reta [10];
public int a;
因此DrawView类具有一个名为ar []的成员。
通常，您可以这样访问它:
DrawView dv = new DrawView();
System.out.println(Arrays.toString(dv.ar)); // dv.ar, not DrawView.ar
当您将其作为DrawView.ar调用时，这意味着该类的所有实例都相同
这就是为什么它说“不能以静态方式引用非静态变量ar”的原因。
当事物“静态”时，它们在该类的所有实例中都是共享/相同/公用的。
所以如果你这样做
公共(public)类DrawView扩展了View {
公共(public)Paint paint = new Paint();
static Reta ar[] = new Reta [10];
public int a;
您所有的DrawView实例都将具有相同的Reta数组:)由于您可能想要多个具有自己的矩形的drawview，因此它应该是私有(private)的。而且当它是私有(private)的时，您不能以静态方式(Class.someMember)而是以实例(classInstance.someMember)或((new class).someMember)为目标。
这意味着...。您决定Reta ar []是私有(private)的还是公开的。
public boolean onTouch(View v, MotionEvent event) {
Ponto2D patual = new Ponto2D((int)event.getX(), (int)event.getY());
Reta r1 = new Reta (inicio, fim);
//DrawView.ar[contador] =rl[]; //offending line
//it should be
//drawView.ar = something; but thats also wrong because you cannot refer to a non-final variable drawView in a inner-class blahblah so here's what you do
((DrawView)v).ar[contador] = rl; //or whatever you want it to be
;)
如果您还有其他问题，请阅读书籍。试试谷歌。 Google您的错误:)所有这些都是非常非常普遍的，已经被覆盖了数千次。