Question

我正在尝试制作一个为每个按钮提供不同工作的android代码。

因此，当用户按下Button1时，Textview字段提供＆＃34;你按下Button1＆＃34;

我的问题是关于我可以实例化Textview ONLY ONCE的正确位置，因为唯一的工作地点在Button1函数内。

单个按钮的Java代码：

 public void Button1(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);
        textView.setText("You clicked the button 1");

    }

总java代码

 public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);
        FloatingActionButton fab = (FloatingActionButton)   findViewById(R.id.fab);
        fab.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)
                        .setAction("Action", null).show();
            }
        });


    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    public void Button1(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);
        textView.setText("You clicked the button 1");

    }
    public void Button2(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);

        textView.setText("You clicked the button 2");
    }
    public void Button3(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);

        textView.setText("You clicked the button 3");
    }
    public void Button4(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);

        textView.setText("You clicked the button 4");

    }
    public void Button5(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);

        textView.setText("You clicked the button 5");
    }
    public void Button6(View view) {
        final TextView textView=(TextView)findViewById(R.id.textView2);

        textView.setText("You clicked the button 6");
    }
}

总XML代码

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/RelativeLayoutID"
    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"
    app:layout_behavior="@string/appbar_scrolling_view_behavior"
    tools:context="com.example.sherifsaleh.xmllayout.MainActivity"
    tools:showIn="@layout/activity_main"
    >

    <Button
        android:id="@+id/button3"
        android:onClick="Button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="3"
        android:layout_above="@+id/button6"
        android:layout_alignLeft="@+id/button6"
        android:layout_alignStart="@+id/button6" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="Button6"
        android:text="6"
        android:id="@+id/button6"
        android:layout_below="@+id/button2"
        android:layout_alignLeft="@+id/button9"
        android:layout_alignStart="@+id/button9" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="9"
        android:id="@+id/button9"
        android:onClick="Button9"
        android:layout_alignTop="@+id/button8"
        android:layout_toRightOf="@+id/button8"
        android:layout_toEndOf="@+id/button8" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="8"
        android:id="@+id/button8"
        android:layout_below="@+id/button5"
        android:layout_toRightOf="@+id/button4"
        android:layout_toEndOf="@+id/button4"
        android:onClick="Button8"/>

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="2"
        android:onClick="Button2"
        android:id="@+id/button2"
        android:layout_above="@+id/button5"
        android:layout_toRightOf="@+id/button1"
        android:layout_toEndOf="@+id/button1" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:onClick="Button5"
        android:text="5"
        android:id="@+id/button5"
        android:layout_below="@+id/button1"
        android:layout_toRightOf="@+id/button1"
        android:layout_toEndOf="@+id/button1" />

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="1"
        android:onClick="Button1"
        android:layout_above="@+id/button4"
        android:layout_alignLeft="@+id/button4"
        android:layout_alignStart="@+id/button4" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="4"
        android:id="@+id/button4"
        android:layout_above="@+id/button7"
        android:layout_alignLeft="@+id/button7"
        android:layout_alignStart="@+id/button7" />

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="7"
        android:id="@+id/button7"
        android:layout_alignParentBottom="true"
        android:layout_alignLeft="@+id/textView2"
        android:layout_alignStart="@+id/textView2"
        android:layout_marginBottom="90dp" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textIsSelectable="true"
        android:text="New Text"
        android:id="@+id/textView2"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="80dp"
        android:textSize="50dp"/>
</RelativeLayout>

Answer 1

试试这样。

public class MainActivity extends AppCompatActivity {

private TextView textView;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    textView = (TextView)findViewById(R.id.textView2);
    ....
}

按钮点击方法

 public void Button1(View view) {
    textView.setText("You clicked the button 1");
}

Answer 2

不确定你的问题是什么。如果您询问在按钮监听器中执行findViewById是否可以接受，那么它是可接受的但不是可选的。每次按下按钮，代码都会运行。在onCreate中做一次

会更好

Answer 3

只需在活动开始时声明它

public class MainActivity extends AppCompatActivity {
      private TextView textView2;
      .....

    protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_layout);

    textView2 = (TextView) findViewById(R.id.textView2);}
    .....
    public void Button6(View view) {

    textView2.setText("bla");
}

这就是你要求的吗？

Answer 4

1）首先尝试在onCreate中初始化你的引用，这些引用加载一次。所以对你的视图的引用只会初始化一次例如 -

 @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btnOne = (Button) findViewById(R.id.btnOne);
        btnTwo = (Button) findViewById(R.id.btnTwo);
        textView = (TextView) findViewById(R.id.textView);

        btnOne.setOnClickListener(this);
        btnTwo.setOnClickListener(this);
}

2）不是为每个按钮调用单独的方法，而是按上面提到的按钮点击监听器

and implement  View.OnClickListener and then

3）覆盖方法

@Override
    public void onClick(View v) {
        Button b = (Button)v;
        String buttonText = b.getText().toString();
        textView.setText("You clicked on  " + buttonText);

    }

所以onClick中的代码在你的情况下重复，而不是每次单独写一次并获取文本，或者你可以设置按钮的标签并获取它（如果你想将另一个值设置为textview而不是按钮文本）并设置为textview，就像我在onClick中所做的那样。它将减少您的工作量并提高代码的可重用性和可重复性.. !!!!!

TEXTVIEW证实地点

4 个答案: