我很难相信我在任何地方都找不到这个答案。我的代码似乎无法正确检查按钮 View 是否存在。这就是我所拥有的，非常感谢任何建议。谢谢!
Java 文件:
public class LayoutsActivity extends Activity {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
ActivateButtons();
}
void ActivateButtons()
{
Button mainLayoutButton = (Button) this.findViewById(R.id.MainLayout);
if(mainLayoutButton != null)
{
mainLayoutButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
setContentView(R.layout.main);
ActivateButtons();
}
});
}
Button linearLayoutButton = (Button) this.findViewById(R.id.LinearLayout);
if(linearLayoutButton != null)
{
linearLayoutButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
setContentView(R.layout.mylinearlayout);
ActivateButtons();
}
});
}
Button tableLayoutButton = (Button) this.findViewById(R.id.TableLayout);
tableLayoutButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
setContentView(R.layout.mytablelayout);
ActivateButtons();
}
});
Button frameLayoutButton = (Button) this.findViewById(R.id.FrameLayout);
if(frameLayoutButton != null)
{
frameLayoutButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
setContentView(R.layout.myframelayout);
ActivateButtons();
}
});
}
Button relativeLayoutButton = (Button) this.findViewById(R.id.RelativeLayout);
if(relativeLayoutButton != null)
{
relativeLayoutButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
setContentView(R.layout.myrelativelayout);
ActivateButtons();
}
});
}
Button absoluteLayoutButton = (Button) this.findViewById(R.id.AbsoluteLayout);
if(absoluteLayoutButton != null)
{
absoluteLayoutButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
setContentView(R.layout.myabsolutelayout);
ActivateButtons();
}
});
}
Button DynamicLayoutButton = (Button) this.findViewById(R.id.DynamicLayout);
if(DynamicLayoutButton != null)
{
DynamicLayoutButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
LinearLayout dynamicLayout = new LinearLayout(LayoutsActivity.this);
dynamicLayout.setOrientation(LinearLayout.VERTICAL);
LinearLayout.LayoutParams size=new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.WRAP_CONTENT);
final TextView mytext= new TextView(LayoutsActivity.this);
mytext.setText("This is the dynamic layout");
mytext.setTextSize(20);
mytext.setGravity(Gravity.CENTER);
dynamicLayout.addView(mytext, size);
/* Button b= new Button(LayoutsActivity.this);
b.setText("Click Here to go to Main Layout");
dynamicLayout.addView(b, size); */
Button b= new Button(LayoutsActivity.this);
b.setText("Main Layout");
b.setId(R.id.DynamicLayout);
dynamicLayout.addView(b, size);
//Step L
Button linear = new Button(LayoutsActivity.this);
b.setText("Linear Layout");
b.setId(R.id.LinearLayout);
dynamicLayout.addView(linear, size);
Button table = new Button(LayoutsActivity.this);
table.setText("Table Layout");
table.setId(R.id.LinearLayout);
dynamicLayout.addView(table, size);
ActivateButtons();
setContentView(dynamicLayout);
}
});
}
}
}
XML 文件:每种布局都有一个，但都很相似
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical" >
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello" />
<Button
android:id="@+id/LinearLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Linear layout" />
<!-- The layout lays out its children next to each other (horizontally or vertically)-->
<Button
android:id="@+id/TableLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Table Layout" />
<!-- The layout represents a table like structure where there are columns and rows for the children-->
<Button
android:id="@+id/FrameLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Frame Layout" />
<!-- The layout places the children on top of one another-->
<Button
android:id="@+id/RelativeLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Relative Layout" />
<!-- The layout positions its children relative to each other-->
<Button
android:id="@+id/AbsoluteLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Absolute Layout" />
<!-- The layout has children with absolute coordinates-->
<Button
android:id="@+id/DynamicLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Dynamic Layout" />
<!-- The layout creates a second, new page -->
<Button
android:id="@+id/MainLayout"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Main Layout" />
<!-- The layout returns to the original layout which seems to be similar to the linear layout-->
</LinearLayout>
最佳答案
我有点困惑。如果您的按钮位于 XML 布局中，它怎么可能不存在呢？如果它不在 XML 中，您的 R.id.MainLayout 将无法编译。除非你说 MainLayout 是某种布局而不是按钮。这也会导致问题，因为您将其转换为按钮。这段代码可以编译并运行吗？
关于java - 如何判断java/android中按钮 View 是否存在，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/10399208/